Glossary

The following list of terms and abbreviations includes many of those that appear
in technical documents on chemical safety, amateur radio, emergency management, Red
Cross activities, and computing, as well as others used on this website. It is not
intended to be a complete list of such terms. Nevertheless, if you find some term
that is not listed here, but which you feel needs definition or a brief explanation,
feel free to contact me. The same applies if you have suggestions for improving
existing definitions. My e–mail addresses are to be found on my
home web page.

Most of the links from within the glossary entries are cross–references
to other entries in the glossary. This avoids multiple definitions of terms, and
reduces the size of the glossary. If you need to see what a linked word in the
definition means, just follow the link, then go back in your browser. When a link
is to another website (outside my own), it is followed by a
"" symbol.

The head entries in the glossary are in alphabetical order. The following index
will take you to the entries that start with the indicated letter. Mouse click on
the initial letter; this will work in any browser.

A scraping of the skin surface. Less severe than laceration. Categorized as:

First degree: involves only epidermal injury. Usually minimal bleeding.

Second degree: involves the epidermis and dermis. Slight bleeding.

Third degree: involves subcutaneous damage; often classed as an
avulsion.

Absorption/absorb

Generally, incorporation of a gas or liquid into a solid by capillary
action, osmosis or the like.
For a person or an animal, absorption is the process of a gaseous or
liquid substance getting into the body through the eyes, skin, stomach,
intestines, or lungs. Compare to
adsorption.

AC (electrical)

Alternating (electrical) Current. A flow of electrical current that flows
alternately in one direction then the other through a conductor, as opposed
to DC. The alternation of direction
generally occurs at regular intervals; the frequency in which the cycle of
direction of flow changes occurs is measured in hertz (Hz) or multiples thereof. The direction
changes twice in each cycle, from (arbitrarily) forward to reverse, then
back to forward. For household AC electricity in the US, this cycle happens
60 times a second; thus it is known as 60 Hz AC. Broadcast
radio signals induce in a
receiving antenna a low-voltage AC
flow, whose base (carrier)
frequency is measured in kilohertz or megahertz.

Acceleration

Rate of change in the velocity
of a moving object with respect to time.
Thus the second derivative of position with respect to time. Symbol is
a; hence, a=d2x/dt2.
See also jerk. Contrary to popular
usage, a slowing of speed is also acceleration, but with a negative value.
Also, since velocity is a vector
quantity, so also is acceleration, and a change of direction even at a constant
speed is acceleration in its physics sense. In
SI units, acceleration
is given as m/s2, though we often see "g" units used, referenced to
the earth's normal surface gravity acceleration:
1 g = 9.80665 m/s2. Acceleration times
mass is
force.

Acclimatization

Physiological and behavioral adjustments of an organism to changes in
its environment.

ACCP

Access Control Coordination Point. The location to which agency
representatives are directed so that they can pass through the
security perimeter at an incident.

Accuracy

The degree to which measurements are close to the actual value being measured.
Contrast with precision
and resolution.

ACGIH

American Conference of
Governmental Industrial Hygienists.
Organization that develops and publishes
BEI®
and TLV®
values. Despite the name, their members may include "anyone engaged in the
occupational hygiene, environmental health, occupational health, or safety
professions even if their primary employment is not with a government agency."

Acrid

An irritating, bitter odor.

Action level

The exposure level, as a
concentration in
air at which OSHA regulations
take effect to protect employees. Exposure at or above this level is
termed "occupational exposure." It is generally set at one half the
PEL concentration.

Active ingredient

A component of a product that directly contributes to the product's
function, as opposed to an inert ingredient.

Acute

Of a medical condition, occurring quickly and for a short time, as opposed
to a recurrent or
chronic condition. Acute
exposure to a substance is contact with the substance that occurs once or
for only a short time (up to 14 days), as opposed to chronic exposure.

Additive

A biologic response to exposure to multiple substances that equals the sum
of responses of all the individual substances added together [compare with
antagonistic effect and
synergistic effect].

Adenine

One of the purine nucleobases in the
nucleotides of
RNA and
DNA, whose structure is shown on
the right. The corresponding nucleosides are adenosine and deoxyadenosine.

ADI

Acceptable Daily Intake. This is the
dose of
a substance which can be consumed every day for a lifetime in
the practical certainty, on the basis of all known facts, that no
harm will result. It is typically measured in mg (of substance)/kg
(of body mass) units. See
also ARfD.

Retention of gas or liquid molecules on the surface of a solid.
"Activated charcoal/carbon," which is finely granulated to give it a
large surface area, is commonly used to adsorb gases. Compare to
absorption.

Automated External Defibrillator. A portable electronic device that
automatically diagnoses the potentially life threatening
cardiac arrhythmias, such as
ventricularfibrillation
and ventricular tachycardia.
The AED treats these conditions through defibrillation: the application of
electrical therapy which stops the arrhythmia. AEDs are designed to be easy
for a layman to use, and the use of AEDs is taught in many first-aid classes.
Contrary to the idea presented in many medical TV programs, a defibrillator
cannot be used to establish a cardiac rhythm if the heart has stopped
completely (asystole).

Aerosol

A suspension of fine solid particles (dust, smoke) or liquid drops
(mist, fog) of a substance in air, small enough to remain suspended for
an extended period of time.

ALA

Short for δ-aminolevulinic acid,
an organic chemical
compound whose structure is shown on the right. When detected, it is
an indicator of lead exposure.

ALARA

As Low As Reasonably Achievable

Alcohol

An organic chemical compound
which has one or more hydroxyl (-OH) groups, each attached to a
saturated carbon atom.
IUPAC names of alcohols have
suffix "-ol" or include "hydroxy". Hence the best known alcohol—part
of alcoholic beverages—is formally designated "ethanol," or more
loosely, "ethyl alcohol" (CH3-CH2OH).

Aldehyde

Also known as an "alkanal." An organic chemical compound containing a formyl
(HC=O) group. See also ketone.

Algebraic (number)

A number that is the root of a finite polynomial in one variable, with
integer coefficients. Symbol
for the set of algebraic numbers is A. All
rational numbers are trivially
algebraic: a/b is the root of bx−a=0, where a and b are integers. An
algebraic number may be complex.
The complementary set to algebraic numbers among the complex numbers is
called the "transcendental" numbers (such as π and e). Algebraic numbers
are an infinitely countable
set, but complex numbers are not, hence "almost all" complex numbers are
transcendental. Algebraic numbers form a
field over the arithmetic
operations.

Aliphatic

Organic chemical compounds
that are not aromatic.
Aliphatic compounds may contain rings, but not those of the aromatic
types. They are more often based on (possibly branching) chains of carbon
atoms. Biological examples are (most) amino acids and all fatty acids.

Allergy/allergic/allergen

A condition in which initially asymptomatic exposure to a substance (called an
"allergen") results in an adverse reaction to the substance at a later
time. It is the result of an inappropriate immune response to an otherwise
harmless substance, and generally results in inflammation. In extreme
cases, an allergy can result in anaphylaxis. Contrast allergy with
intolerance.

ALOHA

Areal Locations of Hazardous Atmospheres. Part of the
CAMEO suite of programs that
indicates how chemicals spread through the air depending on weather
conditions. Developed jointly by the
EPA and
NOAA.

AM (Amplitude Modulation)

In radio terminology, a type of
modulation in which the
signal strength (amplitude) of the
carrier varies directly with that of the signal it encodes, though never
reaching zero. Thus there is always at least a bare carrier to which a
receiver can tune and lock onto.

Amateur (radio)

Literally, amateur means done "for the love of" as opppsed to, for example,
for remuneration. Anateur radio in the US at least is defined by the
FCC as a "voluntary, non-commercial
radio service [that] allows licensed operators to improve their communications
and technical skills...." The FCC goes on to say how this provides the US
with a pool of individuals who can provide emergency communication. Note that
amateur radio operators (informally, "hams") must be licensed by the FCC, a process that
involves examinations that cover the legal and technical aspects of amateur
radio.

Ambient

Refers to existing or normal conditions of temperature, humidity, and
the like.

Amino acid

An organic chemical compound
that has both at least one carboxylic or acid group (COOH) and at least one
amine group (usually NH2). Amino acids are the
basic components of proteins,
and otherwise occur naturally (see example
ALA) and as artificially manufactured
(see example EDTA). The amino acids
in proteins have the amine group attached to the same carbon as the carboxyl
group, and are referred to as α–amino acids, or as 2–amino
acids. Also, except for the simplest one (glycine), the amino acid components
of proteins occur in two mirrored forms and are chiral (that is, they are stereoisomers). As it happens, among those chiral
amino acids, only the L–amino acids—those observing the
CORN Law—are used in earthly
life forms.

Anaphylaxis is a sudden, acute, multi-system, severe allergic reaction. It is a serious medical
condition that can be fatal (approximately 1500 deaths per year in the US).
Anaphylactic shock is a reaction that involves circulatory collapse or
suffocation due to swelling of the trachea or bronchi.

Anesthetic

A drug which causes reversible loss of sensation, either to an organism as
a whole: "general anesthetic"—which usually results in loss of
consciousness—or to a limited part of the body: "local anesthetic."
Contrasted with analgesics, which reduce pain without loss of sensation.

Anemia

A condition in which the blood is deficient in red blood cells (erythrocytes),
hemoglobin or volume.

Anoxia

A condition in which there is relative lack of oxygen in the blood or
tissues.

Antagonistic

A biologic response to exposure to multiple substances that is less
than would be expected if the known effects of the individual substances
were added together [compare with
additive effect and
synergistic effect].

Anterior

The front end of an organism. Usually also the head ("cephalic") and "oral"
(mouth) end, and depending on the specific organism, the "cranial" (skull) or
"rostral" (beak) end. Opposite of posterior.

(Amateur Radio) Automatic Packet
Reporting System. Sometimes rendered as "Automatic Position Reporting
System," though it is a general packet radio system that is only in part used
to report the geographic location of a transmitter. Another major use is
reporting the readings from weather stations.

Aqueous

Having to do with water. An aqueous
solution of a substance
is one with water as the solvent.

ARES®

Amateur Radio Emergency Service, a
Volunteer organization, administered by ARRL, consisting of amateur radio operators who are
trained and equipped to assist with communications in emergencies, as well as
for non-emergency public service events. See also RACES.

ARfD

Acute Reference Dose. This is the
dose of a substance that can
be consumed over a short period of time (usually during one meal or in
one day), without an appreciable health risk to the consumer, based on
all known facts at the time. See also
RfD, and
ADI.

Aromatic

A class of organic chemicals
that, loosely speaking, contain flat ring structures with double bonds.
Most aromatic rings have at least some carbon atoms, but "heterocyclic"
aromatics have nitrogen, oxygen, sulphur, or the like as well. These in
fact are the most common biological aromatics. For a more detailed
explanation, see the Wikipedia article. Contrasted with
aliphatic. Biological
aromatic compounds include sugars,
a handful of the amino acids, and
the nucleobases of DNA and
RNA.

ARRL

American Radio Relay League. A US national
organization that provides information and services to amateur radio operators. ARRL also represents
their interests to US government agencies—particularly Congress
regarding legislation and the FCC
regarding regulations and enforcement—and in international radio
organizations, such as the IARU and
the ITU.

Asphyxiant

A gas or vapor that can cause unconsciousness or death by suffocation
(anoxia). Simple asphyxiants
displace oxygen; chemical asphyxiants interfere with the body's ability
to intake or use oxygen. Asphyxiation is the result of inhaling an
asphyxiant or of choking, drowning, strangulation, apnea or the like.

Asthenia

Loss of strength or energy.

ASTM

The ASTM International.
The organization
formerly known as "American Society for Testing and Materials," (hence
the initialism) that has developed over 12 000 industry technical
standards for a variety of materials, products, systems and services.

Asystole

Cardiac arrest. Commonly
called "flat line," this is a total lack of electrical activity in the
heart, as seen on an electrocardiogram (EKG/ECG) as a straight ("flat")
line.

ATP

Adenosine triphosphate. An organic chemical compound, universally used in
biological cells on Earth as a medium of intracellular energy transport.
The structure of ATP is shown on the right. The upper right-most block
of atoms is the purineadenine, which is attached
to a ribosesugar at the ribose 1' carbon.
Phosphate groups are
ester linked to the left off
the hydroxyl (-OH) group on the ribose 5' carbon (refer to the
diagram). So far, and with just one phosphate, this is one of the
nucleotides of
RNA (viz. adenosine monophosphate).
In both RNA and DNA, the phosphate
group on the ribose 5' carbon then ester links to the hydroxyl on the
3' carbon of the ribose in the next nucleotide in sequence.

Replacing the hydroxyl group on the 2' carbon of the ribose with a
hydrogen (removing the oxygen) turns it into deoxyribose, giving the
deoxyadenosine monophosphate nucleotide that is found in DNA. All other
RNA and DNA nucleotides are constructed and linked similarly, with just
one of the other nucleobases in place of adenine. Typically
for the energy storage function of ATP, the left-most phosphate bond is
broken (hydrolysed),
yielding its binding energy to some cellular process, plus molecules of
adenosine diphosphate (ADP) and phosphoric acid. Alternatively, ATP can
be hydrolysed into adenosine monophosphate (AMP) and pyrophosphate.

Atrium

Plural atria, adjective atrial. The atria are the smaller, upper chambers
of the heart that receive blood from body to be circulated through the
lungs (right atrium), or from the lungs (left atrium) to be circulated
through the body. The atria feed blood to
ventricles, which deliver
the blood.

ATSDR

(HHS)
Agency for Toxic Substances and Disease Registry, created by
CERCLA.
Mission is to serve the public by using the best science, taking
responsive public health actions, and providing trusted health
information to prevent harmful exposures and
disease related to
toxic substances. Specific
agency functions include public health assessments of waste sites,
health consultations concerning specific hazardous substances, health
surveillance and registries, and response to emergency releases of
hazardous substances.

Avulsion

Injury in which part of the body is displaced from its normal location.
An extreme case would be amputation by having the member pulled off.
See also abrasion (third
degree).

BEI®

Biological Exposure Index. Guidance values developed by the
ACGIH for assessing
biological monitoring results. BEIs®
represent the levels of determinants that are most likely to be
observed in specimens collected from healthy workers who have been
exposed to chemicals to the same extent as workers with exposure at
the Threshold Limit Value
(TLV®). There are currently more than 50 of these. For more details
on how this works, see the ACGIH's
Introduction
to BEI®.

Billion

Large number that is ambiguous, and therefore avoided as much as possible
on this web site. In the US, and at least officially in the UK since 1974,
"billion" is taken to mean a thousand million (109). In much
of the rest of the world, including continental Europe and most French,
Spanish and Portuguese speaking countries (Brazil excepted), "billion"
(or a similar word) means a million million (1012). To me, the
latter usage arguably is the more logical, but we live with the language we
have. The same difficulty is to be found also with the larger such numbers:
trillion, quadrillion, quintillion, etc.

There is an unambiguous word for 109, namely "milliard,"
but there are at least two reasons for me not to use it. First, relatively
few English speakers, particularly in the US, will know what it means.
Second, there is no ordinal/fractional number equivalent that I know of.
I mean, "milliardth," really?

Biological agent

A general term for a pathogen.
Examples are prions, viruses, bacteria, protists, fungi, and any of several
multicellular parasitic animals. That doesn't leave much.

BIPM

Bureau international des
poids et mesures (International Bureau for Weights and Measures).
Paris-based standards and metrology agency that is both the French
equivalent of the US NIST and the
overseer of the definition of SI.

BLEVE

Boiling Liquid Evaporating Vapor Explosion [pronounced "blevy"]. The
explosive release of expanding vapor and boiling liquid following the
catastrophic failure of a pressure vessel holding a pressurized
liquefied gas such as propane or LPG, especially when exposed to fire.
Transportation BLEVE incidents involving hazardous substances may pose
significant threats from explosions as well as contamination. A BLEVE
does not require a flammable substance to occur, but in the case of
flammable vapors, a fireball or fuel-air explosion is likely.

BMC, BMD, BMR, etc.

BMC and BMD are respectively the benchmark concentration and dose of an etiological agent that causes a predetermined
change in the response rate of an adverse effect, called the benchmark
rate or BMR. Specifically, BMCLx and BMDLx (e.g., BMDL50) combine
these elements to mean the dose/concentration that produces the change
x in the BMR. The US EPA has
developed
BMDS—BMD Software—that
applies BMD methods to hazardous pollutant risk assessment.

This terminology provides a generalization to multiple possible adverse
effects and effect levels of metrics such as
LC50 and
LD50.
US EPA currently uses BMC and BMD techniques to establish
RfC and RfD values, superseding
the use of NOAEL.

Body burden

The total amount of a substance in the body. Some substances build up
in the body because they are stored in fat or bone or because they
leave the body very slowly.

BOINC

Berkeley
Open Infrastructure for Network Computing. Operated by the
University of California, Berkeley, this system makes idle computational
power of numerous computers throughout the world available for projects in
mathematics and the sciences that require massive amounts of computing.

A substance that reduces the change in
pH that might otherwise occur
when there is an addition of an acid or alkali.

[n–]Butyl acetate

An
organic
chemical compound, a colorless, flammable liquid, whose molecular structure
is shown at the right, and whose name is commonly abbreviated "BuAc." BuAc
is used as the standard reference material for determining relative
evaporation rate, using
the ASTM Standard Test Method
D3539–87 (2004). BuAc is the ester of n-butanol and acetic acid.

C (symbol)

C is used as the symbol in electronics formulas representing electrical
capacitance. C is also
the symbol for the SI derived unit
coulomb, and for chemical
element carbon. C or ℂ represents the
set of complex numbers. In
physics, c (or c0) represents what is commonly
called the "speed of light" with "in a vacuum" implied, but it is more
fundamental than that.

CAA

The Clean Air Act of 1970, as amended.
40 CFR 50–80.
The EPA has enforcement
authority.

CAD

Computer Aided Design. A class of computer applications that allow the
creation and manipulation of graphic images, usually in vector graphics format, but some also handle
raster images.

Calibrate

Adjust a measuring device so that (ideally) it is accurate across its scale to within its indicated
resolution. As a compromise,
it may be adjusted so that it is most accurate within the range of
measurement most commonly used or most critical to an application.

CAMEO

Computer–Aided Management of Emergency Operations. A suite of
programs that assist planners for and responders to chemical
release emergencies. CAMEO Chemicals refers to the database of over
6000 hazardous chemicals that comes with the programs. Other CAMEO
components are ALOHA and
MARPLOT. See also the
CAMEO
information on the
EPA website. The program
is compatible with
LandView.

Capacitance/capacitor/capacitive

Electrical capacitance, symbol C, is the ability of a device known as a
"capacitor" to store electrical energy by means of a static electrical
field; measured in SI units of
farads. An electrical circuit in
which capacitance dominates over
inductance is described
as "capacitive," as is reactance
due to capacitance.

Carbohydrate

Organic chemical compounds
composed of carbon, hydrogen and oxygen, often with a hydrogen to oxygen
ratio of 2:1 (as in water). Typically, they are polyhydroxy (many -OH groups)
aldehydes and
ketones in structure.

In radio terminology, an
unmodulated signal at a
specific frequency, to which
(or near which) a receiver is tuned to receive the information encoded by
the modulation imposed on it.

CAS

Chemical Abstracts Service, a function of Chemical Abstracts,
a scientific journal published by the American Chemical Society (ACS).
They index papers published in the journal by the chemicals referenced
in them, using a numeric coding system, called
"Registry Numbers" (RN). RNs are
commonly used to refer briefly and unambiguously to hazardous materials.

Catalyst

A chemical substance that facilitates or increases the rate of a
chemical reaction without itself being consumed in the reaction.

Catenary

The curve followed by a rope, cable or chain (Latin catena) under its own, uniform weight in
gravity. Mathemarically, the curve is y=a⋅cosh(x/a) =
a/2(ex/a+e−x/a).
Similar in shape to a parabola, with which it was initially confused.

CDRG

Catastrophic Disaster Response Group.

CEC

Community Emergency Coordinator. The individual or agency
appointed by the LEPC who
receives emergency notification of hazardous materials incidents under
the provisions of EPCRA.

Ceiling value

The concentration of
a substance that must never be exceeded at any time in the workplace,
under OSHA regulations.

Cellulose

A complex carbohydrate
polysaccharide, consisting of thousands of glucose subunits. Cellulose forms a large part
of plant matter, especially of plant cell walls. It is indigestible by
humans.

Celsius, degree

Common metric (but not SI) unit
of temperature, symbol Â°C. Named after the Swedish astronomer Anders
Celsius. Once, but not for the last 60 some years, known as the "degree
centigrade." For further details, see entry
kelvin.

Comprehensive Environmental Response, Compensation, and Liability Act,
40 CFR 300. Also
known as the "Superfund"
Act, it provides funds to clean up hazardous materials releases into
the environment The EPA has
jurisdiction over its provisions.

Cerebral

(Somewhat loosely) pertaining to the brain; more precisely to the part
of the brain responsible for the "higher" brain functions such as
sensory processing, motor control, thought, learning, memory, and
language.

CERP

Comprehensive Emergency Response Plan. Developed by the
LEPC to provide detailed
information that would be needed in a chemical release incident. A
requirement of EPCRA.

CERT

Community Emergency Response Team. A group of private citizens
who have trained and equipped themselves so as to be prepared to
help themselves, their families, their neighbors and their
communities in case of local emergencies and disasters.

CFR

Code of Federal Regulations. The set of 50 (as of 2005), typically
multi–volume, documents that contain the text of all current US
government regulations. Available from the National Archives and Records
Administration.

Chelating agent

A chemical, such as EDTA,
DMSA, or
DTPAthat can form a chemical
complex with a metal atom or ion, especially one that is
toxic, and that is generally
hydrophilic. Since the
complex is also water soluble,
it thus can be more easily eliminated from the body. A note of caution:
chelating agents should only be used in known cases of heavy-metal
poisoning, and only under proper medical supervision. These agents are
not specific to any particular metal, and can cause loss of essential
elements. "Chelate" is pronounced like "key-late."

Literally "handed," chiral refers to objects, and specifically chemical
molecules, that exist in two distinct forms that are mirror images of
each other. Human hands are an excellent example, hence the name. In
the case of the chemical molecules, the chirality is often significant
in determining whether the molecule will take part in some reactions. A
pair of chiral molecules are known as "enantiomers" of each other.

Chronic

Of a medical condition, persistent and lasting, and/or developing slowly
over an extended time period, as opposed to recurrent or
acute. Of exposure to a
substance, occurring over an extended period (typically more than
a year).

A colorless, odorless, flammable gas slightly less dense than air,
typically resulting from incomplete burning of carbon compounds. CO in
concentrations above
about 100 ppm (the
OSHA limit for long term exposure
is 50 ppm) is a chemical
asphyxiant,
which severely reduces the blood's ability to carry oxygen by binding
strongly to hemoglobin. It also interferes with mitochondrial respiration
by binding to cytochrome oxidase. Generally bad stuff. Interestingly
though, very small concentrations of CO (< 1 ppm) are normal
constituents of some living organisms, including humans.

CO2 (carbon dioxide)

A dense, colorless, odorless gas. Though relatively
non-toxic
and nonreactive, CO2 can displace oxygen and thus
become a simple asphyxiant or
a fire-extinguishing agent. In smaller atmospheric concentrations, CO2 is
also a greenhouse gas.

Cobblestone

The Cobblestone is a unit of computing credit for validated work done
on BOINC projects. The name
is a (weak) pun on other, similarly named computing benchmark units: the
Whetstone and of course then the
Dhrystone,
combined with a
call-out to Jeff Cobb, a BOINC pioneer. The Cobblestone is defined such
that a computer that operates at 1000 double-precision floating point
MIPS for one day
will accumulate 200 Cobblestones after validation of the work via
duplication by another BOINC user. I know: TMI.

Commutative

The mathematical property of a binary operation in which the order of
the operands is not relevant. Ordinary addition and multiplication are
commutative, whereas subtraction and division are not: For a,b ∈
C, a+b=b+a, but a−b≠b−a (unless
a=b).

Complex (number)

A number with both real
and imaginary number
components. Designated C. Typically means one
in which both components are non-zero. Can be represented as a point on
a plane. Used in electronics to represent impedance.

Concentration

The amount (mass or volume) of
a substance in relation to the mass of, or in a specified volume of, the
containing substance. For hazardous materials in the air, concentration
is typically measured either in micrograms per cubic meter
(µg/m3) or in parts per million
(ppm) by mass
(w/w). Chemical concentrations
of substances dissolved in liquids are typically measured in
moles of solute per liter of solvent.

Condensation

Physically, the transition from a vapor phase of a substance to the liquid phase: the
reverse of evaporation. Chemically, refers to a reaction in which two or
more molecules are combined with the release of one or more water molecules:
the reverse of hydrolysis.

Contusion

Medical term roughly equivalent to eccthymosis or "bruise." A type of
subdermal hematoma in which
damaged capillaries seep or hemorrhage blood into subcutaneous
tissues. Term also applies to
similar deeper injuries to muscle or bone.

COOP

Continuity Of Operations Program/Plan. A set of plans designed to assure
that essential operations of an agency of government, a company, or an
NGO will continue in the face of
natural or human-made or technological disasters.

CORN Law

An observation of and mnemonic for the spatial arrangement of elements of
the naturally occurring chiralamino acids that occur in
proteins. All such amino acids
have four distinct elements attached to their alpha carbon atom. The acidic
carboxyl (COOH) and amine (NH2) groups are obvious, since they
are essential elements of an amino acid. There is also one hydrogen atom.
Except for the simplest amino acid glycine, the last position is held by a
molecular fragment known as a "radical" (symbol R). In space, the four
elements are roughly at the corners of a tetrahedron (triangular pyramid).
If you were to look down at the amino acid moleculefrom above the
α–C hydrogen atom, the other elements, listed clockwise from
the carboxyl, spell out CORN: (carboxyl=CO), radical R, amine N. Neat, huh?

Confined space

Spaces hazardous to an occupant due to limited means of escape combined
with other possible hazards, including exposure to air contaminants or
asphyxiants.

Contagious

A term applied to a disease
which is spread by direct physical contact with a person
infected with the disease or
with secretions from or objects in contact with such a person. By contrast
with inherited diseases, diseases transmitted through a biological
vector, or caused by behavioral
or environmental factors. Often defined in practice by the degree to which
isolation or
quarantine is effective in
preventing spread of the disease.

Coordinate Time

In special relativity, a time interval as measured by an external observer,
denoted by dt, as distinguished from proper time interval (dτ). The ratio of these
intervals is given by the Lorentz
factor (γ).

Corrosive

Causing visible destruction of or irreversible alterations to living
tissue by chemical action at
the site of contact.

coulomb

The SI derived unit of electrical
charge, symbol C. Named for French physicist Charles-Augustin de Coulomb.
The coulomb is equivalent to
6.241 509 629 152 65×1018
charge carriers, particularly electrons, and is defined as an
ampere⋅second (A⋅s).

Countable (set)

A mathematically countable set is one whose elements can be matched one
for one with the natural
numbers (an "infinitely countable" set), or with a subset thereof. Proofs
of the countability of a set range from trivial—the even numbers
are an infinitely countable subset of the natural numbers—to quite
sophisticated, as for the algebraic
numbers. Not all sets are countable, most notably the set of
real numbers. Such a set is
called "uncountable" with "infinite" often implied. Also, clearly number
types which are extensions of the real numbers such as
complex numbers and
quaternions are uncountable.

Cascading Style Sheet. A language used to describe the "presentation
semantics" (the look and formatting) of documents written in a markup
language, such as web pages written in HTML
and XHTML. A CSS file facilitates
applying common global characteristics across an entire web site.

CTCSS

Continuous Tone-Coded Squelch System. Known for short as "tone squelch"
or loosely as "PL," though the latter is strictly a Motorola trade name for
their implementation of CTCSS. In CTCSS, a radio transmitter sends one of
several distinct low frequency (<300 Hz) tones along with the normal
voice signal. Radio voice transmissions only use the range of 300-3000 Hz,
so they are sometimes called "sub-audible" tones, even though they are well
within a normal human ear's audible range. A receiver set to use a CTCSS tone
will only "hear" a radio signal that is sending that tone on its receive
frequency. This can reduce interference between nearby systems that use
distinct tones. By contrast, a receiver set only for
carrier squelch will hear all
sufficiently strong transmissions on its set frequency.

Current

In electronics and related physics, the rate of flow of charge carriers
such as electrons, holes, or ions. In electronic circuits, this is
measured in amperes; in formulas
it is represented by the symbol "I".

CV

Comparison value. Calculated
concentration
of a substance in air, water, food, or soil that is unlikely to cause
harmful (adverse) health effects in exposed people. The CV is used as a
screening level during the public health assessment process. Substances
found in concentrations greater than their CVs might be selected for
further evaluation in the public health assessment process.

CW (Continuous Wave)

Sensu stricto, a
radio
signal of constant frequency
and amplitude—that goes on forever. In amateur radiosensu latiore
usage the last criterion is totally ignored. Well as they say, two out of
three ain't bad. In fact, CW is used as the mode of modulation for transmitting Morse code. The signal
is only on when the dots and dashes of the code are being sent. Also, "CW"
is by synecdoche most often applied to Morse code itself in ham speak.

CWA

Clean Water Act of 1972 and as later amended,
40 CFR 100–140, 400–470.
Regulates discharge of pollutants into surface waters. The
EPA and Army Corps of Engineers
have jurisdiction.

Cyanosis

Blue or purple coloration of the skin and mucous membranes due to
anoxia. The color is
caused by the presence of > 5g/dl deoxygenated hemoglobin in surface
blood vessels. It is thus an indication or symptom of severe asphyxiation and must be treated immediately.

Cytosine

One of the pyrimidine nucleobases in the
nucleotides of
RNA and
DNA, whose structure is shown
on the right. The corresponding nucleosides are cytidine and deoxycytidine.

DA

Disaster Assessment. A few years ago this was taken to mean "Damage
Assessment" within the Red Cross, but the scope of the function has been
expanded to view a disaster's effects as a whole. This would include the
status of utilities and roadway access as well as the traditional look at
damage to buildings. It is done initially as a wide area overview, then at
progressively finer detail.

dalton

Convenience mass unit for
individual atoms or (more commonly) molecules. The dalton, symbol
Da—also referred to as the "unified atomic mass unit" (symbol u) for
short—is defined as "one twelfth of the rest mass of an unbound atom
of 12C in its nuclear and electronic ground state." Related to
mole. You may know of the concept
from school as "atomic weight"
or "molecular weight" although those are of course not measures of weight,
and were typically based on the mass of hydrogen atoms. As Mr Spock might
say, the dalton has been experimentally determined to be approximately
1.660 538 782(83)Ã10-27 kg. It was named for
John Dalton, who first proposed the idea.

DAT

Disaster Action Team. Red Cross team which responds quickly to incidents
that directly affect people, such as home fires. The DAT provides immediate
needed assistance to help those clients get through the first few days, to
include food, clothing, medicine, and housing. A DAT may also respond to
incidents in which only first responders are involved, such as industrial
fires, providing the responders with food, liquid refreshment and the like
("canteening").

dB

Symbol for decibel; the bel, of which the decibel is a tenth, is mostly
unused, but was named for Alexander Graham Bell—not for his work on
the telephone but for his studies on auditory phenomena. The decibel is a
dimensionless logarithmic magnitude of power or of power ratio, equal to
10⋅log10(P/P0),
where P is the measured power, and P0 is the
reference level. A change of 3 dB corresponds very nearly to a
factor of 2 in power, since the common log of 2 is ~0.30103. Half power,
used in determining bandwidth, is -3 dB. A change of 10 dB
is a power factor of 10, 20 dB is a factor of 100, and so on. An
advantage of defining gains and losses of power in decibels is that the
values are additive, simplifying calculations.

DC (electrical)

Direct (electrical) current. A flow of electricity which consistently goes
in one direction through a conductor, as opposed to AC. By convention, electric current flow is
taken to be from a relatively positive voltage to a relatively negative one, and is
nearly instantaneous—it actually occurs at a large fraction of the
speed of light, depending on the conductor. This convention is used
because "positive" and "negative" are historically arbitrary designations,
and despite the fact that the primary electric charge carriers are
electrons, which have a negative charge. The electrons are in fact moving
in the direction contrary to current flow, though at a far slower speed.
In fact, the typical ant can move faster than the average electron's flow
through a solid conductor.

DC

DuPage County Illinois, my home county.

Decon

Decontamination.

Demulcent

A material used to soothe or protect inflamed, irritated mucous
membranes.

Denature

With respect to an organic
chemical compound, such as a
protein, means to change its
properties so as to reduce or eliminate its biological function. This
can be done by heating, radiation, or by treatment with various chemicals.
Also used to mean adding a substance to an otherwise edible or drinkable
material—particularly ethyl alcohol—to make it poisonous or
unpalatable.

Deposition

Change of state directly from
gas to solid, without passing through a liquid phase. The reverse of
sublimation.

Dermal

Referring to the skin. For example, dermal
absorption means passing
through the skin.

Dermatitis

Skin rash; inflammation of the skin.

Detection limit

The lowest
concentration of a
substance that can reliably be distinguished from a zero concentration.

Dynamic Host Configuration Protocol. An OSI layer 7 (application layer) computer
network protocol which provides network devices information such as
their IP address, network mask, and addresses of important servers on
the fly (i.e., "dynamically"), so that devices can be added and
removed without having to administer them separately.

An abnormal medical condition adversely affecting an organism's normal
functions. There are several types, including
pathogenic, deficiency,
hereditary, degenerative, dysfunctional and mental, with substantial
overlap between the categories. Generally, only a pathogenic disease
will be communicable.

Distal

Located farthest (or farther) from the point of origin or attachment.
Relatively distant from the mass of the body. The point of reference
may have to be specified in particular cases. Synonym of "peripheral."
Opposite of "central" or proximal.

DMSA

meso-2,3-dimercaptosuccinic acid.
An organic chemical
compound whose structure is shown at the right. Acts as a
chelating agent for most
heavy metals, and is thus used as an
antidote for poisoning
by lead and mercury, among others. See also the entries for
DTPA and
EDTA.

DNA

Deoxyribonucleic Acid. The genetic material of almost all living
organisms. Some viruses use the closely related but less stable chemical
RNA. DNA codes into RNA directly
and into the amino acid
sequences of proteins via
RNA. DNA is an organic
polymer of four different
nucleotides; the
sequence of those nucleotides provides the codes for the proteins. DNA
is virtually unique to an individual sexually-reproducing organism,
except in the case of identical twins or other clones. Unlike RNA,
DNA normally appears as a pair of linked, complementary strands. These
strands tend to be quite long: the largest human chromosome (#1) contains
approximately 220 million nucleotides in each of its paired strands.
See ATP for an example of the
structure of an RNA nucleotide (adenosine monophosphate), and the change
necessary to produce the DNA equivalent (deoxyadenosine monophosphate).

Dorsal

Towards or on the back or upper surface of an organism. Synonym is "superior."
Opposite of ventral.

Dose

The mean mass of a substance
incorporated into a living being as a ratio to the being's body mass.
Usually measured in milligrams of substance per kilogram of body mass
[mg/kg or parts per million (ppm)]
or in micrograms of substance per kilogram of body mass
[µg/kg or parts per billion—i.e., thousand million— (ppb)].
The concentration
of the substance in specific body
tissues may vary widely. An
"exposure dose" is how much of a substance is encountered in the environment.
An "absorbed dose" is the mass of a substance that was actually
absorbed into the body.

Dose-response relationship

A mathematical model of the changes in body function or health
[response] to the amount of exposure [dose] of a substance.

DOT

(US Federal) Department of
Transportation.
See some DOT functions relevant to materials safety under the headings
PHMSA, the
OET and
RITA. They provide
four-digit numbers used to identify materials for regulation or
transportation, under
49 CFR 172.101,
which numbers can be seen on diamond-shaped placards attached to
vehicles that are transporting these materials.

DRO

(Red Cross) Disaster Relief Operation. An organized activity of
the Red Cross, usually conducted in cooperation with other relief
agencies, that provides essentials (such as shelter, food,
medicines) to victims of a disaster, as well as performing other
relief–related functions.

DSHR

(Red Cross) Disaster Services Human Resources. Like a corporate HR
department, they see to the recruitment, training, and appropriate
deployment in DROs of Red Cross personnel.

DSL

Digital Subscriber Line: techniques used to transfer data at high
speeds over telephone lines, while preserving telephone service.
Most often implemented as Asymmetric DSL (ADSL) in which download
transfers (towards the customer) occur at higher speeds than
uploads.

DST

(Red Cross) Disaster Services Technology. Four related functions,
which provide computer, networking and voice communication for use
by other Red Cross personnel, as well as customer service for those
functions.

DTPA

Diethylenetriaminepentaacetic acid,
(or pentetic acid),
an
organic chemical whose
structure is shown on the right. DTPA is used as a
chelating agent,
particularly as an antidote
for poisoning by actinide radioactive elements. DTPA also has industrial
chelating uses (see the Wikipedia link). See also the entries for
DMSA and
EDTA.

E is used as the symbol in electronics formulas representing
EMF, also known as
voltage. In physics, usually
represents energy.

EAS

The Emergency Alert System. Radio and TV broadcasters and cable
TV stations are required by the
FCC to have
the means to alert their audience when an emergency situation
occurs in their area. Usually announced by a loud beep. Tests
of the EAS end with the familiar message "If this had been an
actual emergency …."

EC50

Median Effective Concentration. The
concentration of a
substance in the environment expected to cause a specified biological
effect on 50% of exposed animals.

ECRV

(Red Cross) Emergency Communications Response Vehicle. Formerly used
within the DST function to provide
computers, networking and voice communication support to Red Cross
operations centers such as DRO
Headquarters and Service Centers where the resources available locally
were limited. My introduction to DST was through my involvement with
these vehicles.

There were 12 such vehicles in the continental US. They provided
VSAT satellite access to the Red
Cross facilities, and carried a variety of computing, networking, phone, and
hand-held radio devices. The vehicles themselves, and much of the associated
supplies, were donated by their respective manufacturers. Many hours of
volunteer effort went into their construction. There were several reasons
for their abandonment: the 2000 Ford Expeditions showed their age by needing
occasional expensive and time-consuming repairs. This of course called into
question their availability when needed to perform. Improvements in technology
made many of their most significant advances obsolescent.

Nevertheless, I drove and operated ECRV 4711, based in Glenview IL,
to numerous public events and Red Cross exercises, on occasion to repair
facilities for as much as a week at a time, and most importantly to seven
Red Cross DROs from MN and WI to NJ and NY.

ED50

Median Effective Dose. The dose
of a substance expected to cause a specified biological effect on 50%
of animals.

Ethylenediaminetetraacetic acid
(or ethylenediaminetetraacetate). A synthetic
amino acid (or acid salt) that
acts as a
chelating agent for many
divalent metal ions, particularly lead (Pb+2).
A diagram of the acid's molecular structure is shown to the right. EDTA
is used medically as an
antidote for lead or
other heavy metal poisoning in the form of the di-sodium salt, chelated
with calcium: Na2Ca–EDTA; as a food
preservative; and as an anticoagulant for stored blood (chelating
Ca+2). See also the entries for
DMSA and
DTPA.

EEGL

Emergency Exposure Guidance Level. An acceptable
concentration of a
substance for unpredicted, single, short–term exposure of a
defined occupational group (such as military personnel) to that
substance. Developed by the National Academy of Sciences,
NRC.

EFATG

Emergency First Aid Treatment Guide.

EHS

Extremely Hazardous Substance(s). A term for substances that
must be reported if stored in sufficient quantity to be a
potential threat. See TPQ for
information on the term "sufficient quantity."

Electrolyte

A substance that in aqueoussolution conducts
electricity. In an animal, these are usually dissolved salts containing
sodium or potassium ions. Electrolytes are also called ionic solutes.
The concentration
of electrolytes in blood affects bodily functions. For example, sodium
and potassium ions are vital to the function of nerves, but too much of
either is dangerous.

Electromagnetic Radiation

Energy radiated from a
variety of physical processes that consists of coordinated variations in
electrical and magnetic fields.
Those fields are oriented perpendicular to each other, and vary in
synchronization. Visible light
is one of the more obvious manifestations of electromagnetic radiation
(called EMR for short). Defining characteristics of an EMR wave are its
frequency and amplitude
(strength of the fields). Frequency ranges from a few hertz for ELF radio frequency signals to X-rays (30 PHz
to 30 EHz) and gamma rays (>30 EHz). All EMR waves in a
vacuum travel at the same speed relative to any observer, called for
historical reasons the"speed of light." An EMR wave is embodied in a
stream of photons. The energy of each photon in an EMR wave is
proportional to its frequency: E=hν, where h is the Planck constant:
6.626 069×10−34 J⋅s,
ν is the frequency in Hz, and E is in joules. The polarization of an EMR wave is
determined by the orientation of its electrical field.

EMA

Emergency Management Agency. A generic term, often used for a local
governmental agency responsible for dealing with emergencies of all
kinds. Similar in meaning to
ESDA.

Emesis / emetic

An emetic is a substance that can cause or induce vomiting (emesis).

EMF

Electro-Magnetic Force, the strength of the "push" of electrical flow
through a circuit, or of the strength of a static field; measured in
volts.

Adjective, indicating the occurrence of an
infectiousdisease in a limited geographic
region for an extended period of time. Compare to
pandemic and
epidemic. Endemic diseases
are often widespread in the affected region and
chronic in the affected
population. Occasionally used as a noun, equivalent to "endemic disease."

Energy

In its sense in physics (which is all this entry deals with), energy is
the work actually or potentially done when a force is exerted through a distance. The
SI derived unit for energy is the
joule. Energy can appear in
different forms, such as kinetic and potential, and have different
sources such as chemical, electrical, thermal, nuclear and gravitational,
but all forms of energy can be converted from one to another. Symbol is E.
Einstein famously equated energy and mass, with a unit conversion factor
of c2.

Entropy

Too complicated a topic to be covered here adequately. I refer you to the
Wikipedia article on the subject
for a start. Entropy has a complex history, and different interpretations
in thermodynamics, statistical mechanics, and quantum mechanics. Symbol is
usually S. S is considered to be non–decreasing in closed systems
(this is the 2nd law of thermodynamics), though this behavior is just a
statistical likelihood, albeit a virtual certainty in non-trivial systems.

Enzyme

Organic chemicals that act as
catalysts for chemical
reactions in biological systems. Most enzymes are proteins, although some are molecules of
RNA, or complexes of protein
and RNA (ribosomes).

EOC/EOF

Emergency Operations Center/Facility. In an emergency, agencies
responsible for dealing with the situation meet in this area of an
ESDA or
EMA office to share information
and coordinate their activities. See also CEOC and SEOC.

US Emergency Planning & Community Right–to–know Act.
This is Title III of SARA,
under the provisions of which all
LEPCs are organized.

Epidemic

Noun and adjective, referring to an occurrence of an
infectiousdisease in a limited
geographic region for a limited period of time. Compare to
pandemic and
endemic.

Epidemiology

The study of the distribution and determinants of
disease or health
status in a population; the study of the occurrence and causes of
health effects in humans.

ERG2012

Emergency Response Guidebook, 2012 edition. Latest issue of the
book issued by DOT, which
contains descriptions of the hazardous materials that may be transported
on North American roads, and of the placards that identify the
materials.

ESDA

Emergency Services & Disaster Agency. A generic term, often used
for a local governmental agency responsible for dealing with
emergencies of all kinds. Similar in meaning to
EMA.
DeKalb County has an ESDA.

Ester

An organic chemical compound
typically formed by the reaction of an organic (carboxylic) acid with an
alcohol. The hydroxyl (-OH)
groups of both components are reduced to a single -O- (oxygen) link, with
release of a water molecule. The IUPAC name of an ester is formed from the alcohol
name with suffix "-yl" replacing "-ol" and the acid name with suffix
"-oate" replacing "-oic". So as an example, the ester of ethanol and
propanoic acid is formally ethyl propanoate. For another example, see
BuAc, noting that "acetate" is a
common (and IUPAC approved)
synonym for the systematic name "ethanoate." Inorganic acids which have
-OH groups, such as phosphoric and sulfuric acids, can also form esters.
See entry phosphate as an
example.

Ether

Generally, an organic chemical
compound in which an oxygen atom joins two organic groups. "Ether" as a
specific designation is the common name for diethyl ether,
CH3CH2-O-CH2CH3, formerly at
least used widely as an anesthetic.

Etiologic agent

Anything that can cause illness. Since it may be a chemical or even
psychological or physical cause as well as a biological one, it is more
general term than pathogen.

Evaporation Rate

In the terms used for MSDS,
it is the ratio of the rate at which the substance described in the
MSDS evaporates (changes state
from a liquid to a gas) to the rate of evaporation of a standard
chemical:
n-butyl acetate, under
standard conditions, as specified by the
ASTM as Standard Test Method
D3539–87 (2004). Evaporation rate information can be
useful in evaluating the health and fire hazards of a material.
For example, a substance with a high evaporation rate will readily
form a vapor that can be inhaled or that can explode. Since evaporation
rate is a ratio of like terms, it has no units. Substances with an
evaporation rate greater than 3 are considered "fast" evaporators;
those with a rate less than 0.8 are considered "slow."
N-butyl acetate itself, whose evaporation rate is by definition
1, is considered "medium."

EVC

Equilibrium Vapor Concentration. The limiting atmospheric
concentration of the
vapor phase of a substance in
contact with the liquid (or solid) phase of the same substance, at a
specified temperature (typically "room temperature"—25 ℃).

exaFLOP

A quantity of 1018 (a million million million) basic
floating point computer
operations, such as addition, multiplication and comparison.

US Federal Aviation Authority. Among other things, regulates
and controls quantity and packaging of substances sent by
air.

farad

Named for Michael Faraday, this is the
SI derived unit of electrical
capacitance, symbol F.
It is equal to a coulomb per
volt, to a second per
ohm, or in SI base units:
kg-1⋅m-2⋅s2⋅A2.
A one farad capacitor is quite large. Most capacitors used in electronic
circuits are measured in fractions of microfarads (µF) or in
picofarads (pF).

Fat, fatty acid

A fat is an organic chemical
compound that is an ester of
aliphatic (carboxylic) acids
with glycerol. Glycerol is an alcohol with three active hydroxyl (-OH) groups,
hence a "triol." Each hydroxyl binds to a fatty acid: that is an organic
acid with a chain of carbon atoms. There are usually an even number of
carbon atoms from 4 (butyric acid) to 28. The fatty acids are either
saturated or unsaturated.
The structure of glycerol (also known as "glycerine") is
CH2OH-CH2-CHOH-CH2-CH2OH.

Some fatty acids are described as "essential." These are ones that humans
cannot produce for themselves, at least in sufficient quantities. Those
fatty acids must therefore be obtained from the diet. Examples of
essential fatty acids are linoleic and alpha-linolenic acids; both are
readily available from plants.

FCC

US Federal Communications
Commission. The
government agency responsible for regulating the cable, phone, satellite,
radio and other communications
media within the US and its possessions and between those and other
countries. The Commission's regulations are contained in Title 47 of the
CFR.

FEMA

US
Federal Emergency Management Agency. FEMA is part of the
Department of Homeland Security's Emergency Preparedness and Response
Directorate. FEMA works in partnership with other organizations
that are part of the nation's emergency management system including
state and local emergency management agencies, 27 federal agencies and
the American Red Cross. FEMA's mission is to lead the effort to prepare
the nation for all hazards and effectively manage federal response and
recovery efforts following any national incident. FEMA also initiates
proactive mitigation activities, trains first responders, and manages
the National Flood Insurance Program and the U.S. Fire Administration.

Fibrillation

Generally, uncontrolled and usually rapid twitching of muscle fibers,
with little or no overall muscle movement. In paritcular, as in
ventricular or
atrial fibrillation (aka
V-fib and A-fib), the uncoordinated contraction of the heart muscles,
making them quiver rather than contract properly. By contrast with
tachycardia, which
can be a consequence of A-fib, ventricular fibrillation is a serious
medical emergency, both because blood is not being circulated, and the
condition can easily and quickly degenerate to
asystole.

A mathematical (algebraic) structure that is one step up from a
ring, in that it has all the
properties of the commutative ring, plus one more: the second
(multiplication-like) operator must also have an inverse within the set,
except for the zero (additive identity) element. That is to say that for
any set element a (≠0), there is an element b, such that a⋅b=1
(the multiplicative identity element). This is obviously not true for the
set of integers, but it is for rationals (ℚ) and higher (real,
complex) number types. This means that both operators must have the
closure, associative, commutative, identity and inverse properties, and
the second operator must be distributive over the first. For details on
those properties, refer to the glossary entry for ring.

As with groups and rings, the
set for a field may be finite. Fields with finite sets are known as
Galois fields.

As you may have noticed, I tend to think as a mathematician. So I must
acknowledge at least two other meanings for "field." In physics, a field
is the assignment of a value to every point in a space. That's pretty
general, but so are fields. A weather map showing precipitaton (scalar
value) or wind speed (vector
value) on a two dimensional map is a field. So is the gravitational field
(tensor value) at each point in
spacetime (four dimensions). Lots of options. Another important use of
"field" is the computer sense of a location within a data record that holds
a specific value, say last name or cell phone number.

Floating point / FLOP

A number, usually as stored in a computer, that approximates a mathematical
real number, as opposed to an
integer. Such numbers are often
called "real" in computer programming languages, though they are
strictly only a subset of rational
numbers, even within their limited range. A FLOP (floating point operation)
refers to a basic computation performed by a computer using these numbers,
such as addition, subtraction, multiplication or comparison. (Division is
usually done by multiplying the numerator by the computed reciprocal of the
denominator.)

FM (Frequency Modulation)

A mode of radio signal
modulation in which the
the frequency of the
continuously transmitted carrier
signal varies in response to changes in the amplitude of the signal it is
encoding. Compare to AM.

FOIA

Freedom Of Information
Act —
5 U.S.C. §552, under which citizens can request certain kinds of
information from public agencies. For security reasons, information on
Tier II sites in DeKalb
County must be requested under FOIA.

Force

In physics, an influence that causes a massive object to undergo a change
of velocity (i.e., to
accelerate),
or to undergo a strain.
The SI derived unit of force is the
newton. Symbol is F,
hence F=m⋅a.

FPD

Fire Protection District.

FRP

Federal Response Plan.

Frequency

The rate, in number of full cycles per
second, at which an electrical signal changes. Units are in inverse seconds
(s-1), hertz, or particularly
for radio–frequency signals, in
multiples thereof (kilohertz, megahertz, etc.)

FTP

File Transfer Protocol, an OSI level 7
computer network protocol used to
copy a file over a TCP/IP-based
network, such as the Internet.

Gamma (γ)

Gets lots of uses. Among there are:

Symbol for a photon.

Gamma radiation, otherwise generally known as electromagnetic radiation (light), and
particularly to the highest frequency such radiation
(>30 EHz).

The Lorentz factor, the ratio of coordinate time to proper time intervals dt/dτ in special
relativity: γ =
(1−v²/c²)−½.
A factor in many relativistic equations, such as that for
momentum.

GHz

SI symbol for gigahertz. An
electronic signal of 1 gigahertz varies in cycles which recur
one thousand million (109, US: one billion) times per
second.

GIMP

GNU Image Manipulation Program. A free, open-source digital image
creation and editing tool, available on most computer platforms. It
comes standard on Linux distributions, and can be downloaded in
versions for Windows and Mac.

GIS

Geographic Information System. A computerized mapping system
that divides geographic and statistical data into viewable layers
that can be removed or included depending on the user's needs.

[D-]Glucose

The most common simple sugar in nature. See its chemical structure
on the right. It is a hexose (formula C6H12O6)
It appears not only as a component of "sugars"
sensu lato,
but also in widely distributed polysaccharides such as
cellulose and
starch. The D-
stereoisomer of
glucose is the only one common in nature; consequently, glucose is
also known as "dextrose".

GPS

Global Positioning System. The complex of satellites, ground stations
and receivers used to tell people where and when they are, with potential
accuracy for ordinary users
of a few meters horizontally and vertically, and fractions of a
microsecond. GPS receivers used by people on the ground are often
loosely called "GPSes." The US military runs the satellites and ground
stations, and has an encrypted higher-accuracy system as well.
WAAS has made the civilian
system nearly as good, such that it can be used to land aircraft within
the region it covers.

Group

A mathematical (algebraic) structure that has two elements: a set, and a
binary operator that acts on pairs of members of the set. An example is the
set of integers and the addition
operator. There are four properties that a group must have. (1) Closure:
the result of applying the operator to any two set elements must be in the
set also. (2) Associativity: when there are two or more uses of the operator
in a row, the order in which the operators are applied is irrelevant; in
general the order of the set elements is relevant unless (like
the example integer/addition group) the group is
commutative (aka abelian).
(3) Identity: there is an "identity" element such that any element is
unchanged if combined with it via the operator. For the example group
the identity element is the number zero. (4) Inverse: for any element a of
the set there is an inverse element b such that applying the operator to
a and b gives the identity element. For the example group the negative
integers are the inverses of the corresponding positive integers (and vice
versa).

Note that the group's set may be finite. In particular, the set of integers
{0, 1, ... n} with n>1, designated Zn,
together with addition modulo n forms an abelian group, known as a cyclical
group. As with the example above, the identity element is zero. The inverse
of element a is n−a, and is unique.

Guanine

One of the purine nucleobases in the
nucleotides of
RNA and
DNA, whose structure is shown
on the right. The corresponding nucleosides are guanosine and
deoxyguanosine.

GUI

Graphical User Interface. Arguably by far the most common way for people
these days to interact with computers. Smart phones and GPS receivers to tablet computers and laptops to
desktop computers use graphical displays to get user input and display their
results. Systems like X Window System
and internet web browsers provide graphical remote access over networks to
other computers' applications and resources. Gone are the days of DOS command
lines and text only output on 80–column by 25–line displays (much
less punched cards and line printers), all of which I most definitely do not
miss.

H (symbol)

H is the SI symbol for the
henry. H is also the symbol for the
chemical element hydrogen. In mathematics, H or
ℍ represents the Hamiltonian (quaternion) numbers. Forms of H are used, since Q
is already assigned to the rational numbers. In physics, ℎ represents
the Planck constant, and ℏ represents the Planck constant divided by
2π.

Half–life

The period of time required to
reduce the concentration
of a substance by one half. In the environment, the half–life is the
time it takes for half the original amount of a substance to disappear when
it is eliminated, or changed to another form by radioactivity, bacteria,
fungi, sunlight, or other chemical or physical processes. In the human body,
the half–life is the time it takes for half the original amount of
the substance to disappear, either by being changed to another substance or
by leaving the body.

Ham

Informal designation of an amateur
radio operator. The etymology of the term is disputed.

Hamiltonian (number)

A form of number named for William Rowan Hamilton, the mathematician who
described it. See quaternions.

A protein containing iron in the
blood of most vertebrate animals, contained within red blood cells (erythrocytes).
Hemoglobin is responsible for transporting oxygen from lungs or gills to all the
body's tissues to support aerobic
metabolism. This is far more efficient than transport by dissolving oxygen in the
blood fluid itself. A shortage of hemoglobin, often due to iron deficiency, is a
common cause of anemia.

henry

Plural "henries," and named for Joseph Henry, this is the
SI derived unit of electrical
inductance, symbol H.
It is equal to an ohm⋅second,
or in SI base units:
kg⋅m2⋅s-2⋅A-2.

HF

High Frequency radio waves, specifically those with frequencies of
3-30 MHz, or wavelengths of
10-100 m. In informal usage among
hams, the amateur radio 160 m band is lumped into HF (strictly,
it's MF—Medium Frequency).

Hazardous Materials. See also "HazMat." A hazardous material includes any
substance that is a health or physical hazard as defined by
OSHA. OSHA Regulations
require that an MSDS be kept
on hand for all hazardous materials. Such a substance may harm or
injure humans, animals, agriculture, structures, waterways, highways,
the environment, or other public or private property.

HMEP

Hazardous Materials Emergency Preparedness.

Homogeneous

Uniform in composition throughout a mass of material, at all relevant
measurement scales. Not "lumpy."

HTML

HyperText Markup Language.
Versions of html (latest is 5) are the most widely used computer languages
for developing web pages. I prefer to use the closely related
XHTML for its more rigorous
syntax. For both, elements of the web page are created using tags
. One such tag, which starts "<img", allows inserting of a
graphics image. Amother, <em> (emphasis), on an English language
web site, typically causes the following text to be in italics.
Most html tags have a matching close tag. For the em tag that is
</em>, which indicates return to normal type. Exceptions are like
the self-contained img tag, which ends in " />". The overall format of
a web page can be specified using
CSS.

The splitting of a chemical compound into two parts by the addition of
a water molecule. Examples from this glossary are the reduction of
ATP to ADP, and the separation
of disaccharides (such as sucrose
and lactose) and polysaccharides (such as cellulose and starch) into their simple sugar components.
Such hydrolysis of organic molecules often requires a
catalyst, whereas inorganic
ionic molecules will typically hydrolyse when they dissolve in water.
The inverse reaction, forming a single molecule from two or more with the
release of one or more water molecules is known as condensation.

Hydrophilic

Generally, "compatible with water." Can mean that a substance easily
absorbs, is wetted by, or dissolves in water. As opposed to
"hydrophobic."

Hypertext

Text, such as is typically found on web sites, that contains links to other
information; thus a kind of multi-level text. Look right around here for
numerous examples. The links are known as "hyperlinks."

Hz

Symbol for hertz, named for Heinrich Hertz. Plural of hertz is also
hertz. The hertz is the SI
derived unit of frequency,
equivalent to an inverse second
of time (s-1). An
electrical signal with frequency 1 Hz varies in a cycle that lasts
one second; the cycle of a 10 Hz signal lasts a tenth of a second.
Only audible frequencies (roughly 20-20 000 Hz for humans) are
usually given in Hz. Nearly all
radio frequencies use the
multiples of kilohertz (kHz),
megahertz (MHz), and gigahertz
(GHz).

I (symbol)

I is used as the symbol in electronics formulas representing electrical
current. For that reason,
electronics type people tend to use j instead of i to represent the unit
imaginary number, the
square root of -1. I or ⅈ represents
the set of all imaginary numbers: a⋅i, where a is any
real number.

IARU

International Amateur Radio Union.
A confederation of national amateur radio organizations, such as
ARRL in the US. It provides a forum
for discussion of common issues.

ICP

Incident Command Post. Location from which an Incident Commander
operates under the ICS.

ICS

Incident Command System. The mechanism used to coordinate the
activities of multiple agencies responding to a disaster, led by an
Incident Commander (IC). For more details on ICS, see this web site:
What is an Incident
Command System?
ICS is widely used today on a local level, but is
supplemented by the UCS, and is
being replaced on a national level by
NIMS.

IDLH

Designates the
concentration of a
hazardous material that is Immediately Dangerous to Life or Health.
Values were determined by
NIOSH.

IDNS

Illinois Division of Nuclear Safety. A part of
IEMA,
IDNS is responsible for
protecting Illinois residents from the potentially harmful effects of
ionizing radiation.

Intermediate Frequency. A frequency
different from the native frequency of a
radio signal, to which the signal is converted for ease in processing. Very
high frequency signals, as from satellites, require specialized and expensive
means to carry the signal to where it will be used. Conversion to
lower–frequency IF allows it to be carried by coaxial cable. Also, signal
processing is improved if all possible external frequencies are first converted
to a single IF (via mixing with a local oscillator).

Imaginary (number)

A number which when multiplied by itself ("squared") yields a negative number.
Designated I. All real numbers—positive or negative—by contrast
always give a positive number in this case.

The number of new cases of
disease in a defined at-risk
population over a specific time period or more usually as the fraction or
percentage of that population getting the disease (incidence rate). A
measure of morbidity.
[Contrast with
prevalence].

Incision

A wound, often deep, caused by a sharp object like a knife, razor, or
fragment of broken glass. Usually linear, unlike a
laceration.

Incompatible

A combination of two or more chemicals that gives an undesired reaction
when mixed. This usually refers to a mixture that will react to cause an
imminent threat to health and safety through an explosion, fire, and/or
formation of toxic materials.
The MSDS for a substance is
supposed to list its incompatibilities. But be aware that even ordinary
household chemicals—notably bleach and ammonia—can be
incompatible.

Incubation period

The interval between the time of
infection by a
biological agent and the
time of first appearance of indications or symptoms of infection. Depending on the agent,
this can be hours to decades. For longer incubation periods, a mean and
variance provide a more useful description. Compare to the related term
is latency period.

Inductance/inductor/inductive

Electrical inductance, symbol L, is the ability of a device known as an
"inductor" to store electrical energy by means of a magnetic field;
measured in SI derived units of
henries.
An electrical circuit in which inductance dominates over
capacitance is described
as "inductive," as is reactance
due to inductance.

Infarction

Death of biological tissue
caused by lack of oxygen due to a blood flow blockage (in turn due to a clot,
constriction of blood vessels, hernia, tumor or the like). The mass of dead
tissue resulting from this trauma is called an "infarct." Can affect any tissue
or organ, but commonly known examples affect the brain
(cerebral infarction or "stroke")
or heart (myocardial infarction
or "heart attack").

Infection, infectious

Infection is the colonization of a host organism by an invasive
biological agent which
causes detriment to the host, typically a
(pathogenic)
disease. Also typically, the
invasive agent uses the host to reproduce and propagate itself. A disease
caused by an infection is called "infectious."

Infectivity, infective

The ability of a pathogen to
establish an infection by horizontal transmission, viz. not parent to child.
A pathogenic disease with a short
latency period and a high
virulence must generally also
be highly infective to maintain itself. Contrast infectivity with
transmissibility.

Infrared

"IR". The part of the electromagnetic
radiation spectrum that is longer wavelength than that of visible
light, that is, longer than about
750 nm and shorter than radio
frequencies. This latter limit is somewhat fuzzy: infrared is often
taken down to a wavelength of 1 mm, but there is a sub-millimeter band
in the radio spectrum. Both are extremes. "Near" infrared radiation—that
is, near to visible light—is sensed as heat. Human body temperature
radiates infrared at around 10 µm (as long-wavelength infrared).
About half of sunlight power is in the infrared; most of the rest is visible.

Integer (number)

A number—positive, negative or zero— that has no fractional part.
Designated Z or ℤ. The integers form an
abelian (i.e., commutative)
group with addition as the operator
element. It also forms a ring with
second operator element multiplication. It is the smallest non–cyclical
group and ring based on the natural
numbers.

Intolerance

Also known as non-allergic food
hypersensitivity. A negative physiological reaction, immediate or delayed,
to a food or food component, that does not involve an immunological
response. Examples are lactose and fructose intolerance, and sensitivity
to peanuts. Intolerance can be due to a metabolic error in processing
normally tolerated nutrients, such as diabetes, phenylketonuria, or lack of
lactase (the last of which may be perfectly normal in adults from some
regions).

IOMA

Illinois Open Meetings
Act. Requires government
agency transparency in their activities, in most cases allowing public access
to their deliberations. All DeKalb County LEPC meetings are conducted in accordance with this
law.

The earth's upper atmosphere, from about 50 km up. So called because
solar radiation—especially UV
(ultraviolet) and shorter wavelengths of light—causes air molecules to lose some of their
electrons, thus becoming ionized. Among other things, the resulting layers of
ionized gas can reflect (strictly speaking, "refract") radio waves, as long as
the waves do not exceed the MUF, thus allowing them potentially
to travel around the world—or at least beyond the line of sight.

IPC

The Illinois Poison Center. Serves all of Illinois 24 hours a day, 365
days a year. Staffed by nurses, physicians, pharmacists and other poison
specialists, the IPC offers free, confidential poison prevention advice
and treatment recommendations via a toll–free hot line,
1–800–222–1222. The IPC also has informative and
preventative information at
their website.

ISFI

Illinois State Fire Institute. Provides training for fire fighters.

Isolation

The segregation from the general population of an individual
infected with
a contagious disease, to prevent
further spread of the disease. The one
infected can be a human, or possibly another animal. Distinguished in strict
usage from quarantine, in
that an isolated individual is usually known to be infectious. An exception
to this is "reverse isolation" in which a person who is susceptible to
disease is kept isolated from potential carriers. Isolation of humans is
most often to be found in health-care facilities such as hospitals.

ITU

International Telecommunications Union. A UN agency responsible for coordinating
the global use of the radio spectrum,
the development of technical standards, and similar technical functions.

IUPAC

The International Union of Pure and Applied Chemistry. An international group
representing national organizations of chemists. Perhaps best known—and
in this document, exclusively so—for its standardized system of chemical
nomenclature, particularly for organic
compounds.

J (symbol)

J is the SI symbol for
joule. In physics, j
represents Jerk. Electronics types
often use j instead of i as the
imaginary number unit.

The time rate of change of
acceleration.
Symbol j. Thus the third derivative of position with
respect to time: j=d3x/dt3.
Jerk times mass is known as Yank,
symbol Y. Further time derivatives of position are known
as snap: s (4), crackle: c (5) and
pop: po (6). The last has to have a two-letter symbol
since "p" is already used by momentum. Not kidding. Not much, anyway.

JIC

Joint Information Center. Common source for several organizations and
agencies to provide coordinated and verified information to the public
in the case of an emergency.

joule

Symbol J; named for James Prescott Joule. The
SI derived unit of energy or work.
By Newton's formula equating work with force (in units of
newtons) times distance, this
works out to SI base units of kg⋅m2⋅s-2.

K (symbol)

K is the SI symbol for
kelvin. K is also the chemical
symbol for potassium.

kelvin

Symbol K; named after William Thomson, Lord Kelvin. This is the
SI base unit for temperature. It is
defined such that the thermodynamic temperature of the triple point of pure,
standard (VSMOW) water is
273.16 K—0 K is absolute zero, so all values on the kelvin
scale are positive. Note first that the unit is called the "kelvin,"
not the "degree kelvin" and the symbol has no degree (°) mark.
Secondly, the everyday metric unit for temperature, the degree Celsius (symbol ℃), is defined such
that an interval of one ℃ is one kelvin; the zero point for ℃
is 273.15 K, not the freezing point of water. This in effect
defines the triple point of water as 0.01 ℃.

Ketone

An organic chemical compound in
which two carbon-containing groups are joined by a carbonyl (C double-bonded
to O, in print usually designated C=O). If the carbonyl group is at the end
of a group instead of joining two groups, the result is an
aldehyde.

kHz

SI symbol for kilohertz. An
electronic signal of 1 kilohertz varies in cycles which recur
one thousand times per second.

kilogram

The SI base unit for
mass, symbol kg.
This is in at least two respects unusual among SI units. For one, its name
and symbol include a multiplicative prefix (kilo, k). For another, it is the
only SI unit still defined by a physical prototype. This latter means that it
uniquely cannot be duplicated by instruments in a metrology laboratory other
than at BIPM, where the international
kilogram prototype is kept. Others must rely on carefully replicated and
maintained secondary standard kilograms. This is awkward to say the least; I
understand that talks are underway to see how we can get away from this mode
of definition (as was done earlier with the
meter), so stay tuned.

Kinetic rate coefficient

A number that describes the rate at which, for example, an air pollutant
reacts.

KSA

Knowledge, Skills, and Abilities.

L (symbol)

L is used as the symbol in electronics formulas representing electrical
inductance.

Laceration

An irregular tear-like wound, often caused by blunt trauma, such as scraping
more severe than an abrasion.
Not to be confused with an
incision.

LAN

Local Area Network. A network that provides data links for computers
that are located within a limited geographical area, typically a single
building or a campus. Today, typically implemented in Ethernet and/or
Wi-Fi. Contrast with
WAN.

LandView

A GIS from the US Census Bureau
that can be used with
MARPLOT to estimate the
number of people affected by a hazardous materials release. See also
CAMEO.

Latency period

The time interval between exposure to an
infectiousbiological agent or
a toxic substance and the
first manifestation of illness caused by that agent or substance. May
range from a few seconds for toxic substances or hours for biological
agents to decades for either. In the case of an infection, the latency
period is often taken to be the interval between the time of infection
and the time the infected host becomes itself infective. Compare the
related term incubation period.

Lateral

Towards the side of an organism on the left-right axis. Opposite of
medial.

LC50

Median Lethal Concentration. The
concentration value
of a hazardous material at which 50% of animals would be expected to
die from its effects; a calculated value.

LCLO

Lethal Concentration LOw. The lowest
concentration of a
hazardous material at which death occurred.

LD50

Median Lethal Dose. The dose
of a hazardous material at which 50% of animals would be expected to
die from its effects; a calculated value.

LDLO

Lethal Dose LOw. The lowest
dose of a hazardous material
at which death occurred.

LEL

Lower Explosive Limit. The atmospheric
concentration of a
flammable hazardous material below which it lacks sufficient fuel to be
subject to explosion. Also known as the Lower Flammable Limit (LFL).
See also UEL.

LEPC

Local Emergency Planning Committee. A group responsible for
developing plans to deal with release of hazardous materials.
In Illinois, there is an LEPC for every county, established by
IEMA, the
SERC for Illinois. The legal
provisions for LEPC organization are part of
EPCRA.

Lesion

An abnormal change, injury or damage to an animal or plant
tissue. Lesions are typically
caused by trauma or disease, but may be induced deliberately in surgery.

Light

Usually refers to the part of the EMR
spectrum that is visible to humans, a wavelength range of roughly 380 nm
(violet) to 750 nm (red). Light slightly shorter than this range is known as
ultraviolet; many longer wavelengths
are designated infrared. The boundaries
are a bit loose, since some animals can see well into the infrared and
ultraviolet ranges, and there is even some variation within humans.

liter (or litre)

Common metric (but not SI) unit
of volume, equal to a cubic decimeter. There are thus 1000 liters in a
cubic meter (m3). There is no standard symbol for liter, but
L is often used, as well as a script lower-case l.

LOAFL

Lowest Observed Adverse Effect Level. The lowest tested
dose of a substance that has
been reported to cause harmful (adverse) health effects in people or
animals.

LOC [plume]

Level Of Concern. In the context of hazardous materials
releases, the maximum TWA
atmospheric
concentration of a
substance to which members of the general public can be exposed, for a
specified period of time (typically 15 minutes). For smoke,
for example, the LOC concentration is
150 µg/m3 for up to
1 hour. For hazardous materials, the LOC is usually set at
0.1 times the IDLH value.

An "LOC plume"
is the volume of dispersed substance in the air that exceeds the LOC
concentration.

M (symbol)

Symbol for the meter, the
SI unit of length is m; m is
also the symbol in physics for mass.

MAA

Mutual Aid Agreement.

MABAS

Illinois Mutual Aid Box Alarm System. An organization of more
than 1000 fire-fighting departments in Illinois, southern Wisconsin, and
parts of Indiana, Iowa and Missouri. MABAS provides a mechanism for fire
fighters, EMS personnel
(EMTs) and specialized teams (such
as Search and Rescue and HazMat)
to get assistance from other FPDs
as required. MABAS also serves IEMA
as an Illinois statewide emergency resource, since the state has no fire
department of its own.

Maltose

A disachharide sugar made by
chemical condensation of
two glucose units. It is commonly
formed in the hydrolysis
of starch by the enzymeamylase. Amylase also produces some of the trisaccharide
(or oligosaccharide)
maltotriose, condensed from three glucose unita. Both maltose and maltotriose
are in turn hydrolysed to glucose by the enzyme maltase.

MARPLOT

Mapping Applications for Response, Planning and Local Operational Tasks.
Part of CAMEO, jointly
developed by the EPA,
NOAA, and the US Census
Bureau. A GIS that shows areas
affected by a HazMat
incident on street–level maps. See also
LandView.

Mass

IMO one of the most slippery of physical concepts
(time takes the cake).
Primarily mass is a measure of an object's inertia—that is, as how
much force it takes to change
the object's state of motion. Fine, but force is then defined in terms of
mass and change of motion. Circular? Blame Newton. "Gravitational mass"
would appear to be an obsolete concept, given general relativity, wherein
any object in the same inertial frame of reference will follow the same
geodesic in spacetime, regardless of mass. In any case, the
SI base unit of mass is the
kilogram, though other units
are used for specific applications. See the entry on the dalton for example. Distinguish mass from
weight. The symbol for mass in
physics formulas is m.

Matrix

Mathematically, a rank 2 tensor:
aij, but more usually notated
am,n. Simply described, that is a table with m rows and
n columns. If m=n, it is a square matrix; otherwise it is rectangular.
If m=1 it is a row vector;
if n=1 it is a column vector.

Medial

Towards the center of an organism on the left-right axis. Opposite of
lateral.

Routine aviation weather report (the term "METAR" is an acronym for the
French equivalent phrase). A compact, internationally recognized format for
routine—usually hourly and automated—weather reports, typically
from airport locations. The report shows a location code, day of month and
(UTC) time, dry bulb and dew point
temperatures (Â°C),
precipitation, cloud cover code(s) and height(s), wind compass direction
and speed (m/s or knots), visibility (km or statute miles), and the like.
Geared towards aircraft pilots, but obviously also of general interest.

meter (metre)

The SI base unit of length. Symbol
is m. Defined as the length of the path traveled by light in a vacuum
during a time interval of
1/299 792 458 of a second (symbol s). Note that this in effect
defines the speed of light in a vacuum as exactly 299 792 458
m/s. The definition has been through changes over the years. Originally
(and still very nearly) it was the fraction 1/10 000 000 of
the distance on the longitude of Paris between the earth's north pole and
equator. Thus the circumpolar circumference of the earth is very nearly
40 000 000 m. For a while, it was defined by marks on a
bar kept at BIPM, then in terms of
wavelengths of atomic radiation—but a different one than used for the
second.

MHI

Material Hazard Index. A number used to rank chemical materials
to determine the level of controls necessary for regulation. MHI
is determined by dividing the
EVC of a material at
25 ℃ by the LOC
value for that material in the same units.

MHz

SI symbol for megahertz. An
electronic signal of 1 megahertz varies in cycles which recur
one million times per second.

micrometer/Micrometer

[1] Spelled micrometer/micrometre, and pronounced "MIKE ro me ter",
the length of one millionth (10-6) of a meter, symbol μm. [2] Spelled with
unspecified initial capitalization, and pronounced "my KROM eh ter"
it is a generic, relatively high
resolution length
measuring
device occurring
in various forms. Micrometers (second meaning) which incorporate a
vernier scale, can
measure to 10-4 inches or 10-6 meter (i.e., to
a micrometer, first meaning); though to achieve those levels of
accuracy requires very
careful manufacture and calibration. Without a vernier scale, the
resolution of either type of micrometer [2] is one digit less.

MIPS

Million [computer] Instructions Per Second, a measure of a computer's
processing speed.

Modulation

In radio and electronics
terminology, the process by which information is embedded in a signal.
Without radio modulation there would only be a bare carrier, or (as with modulation techniques
such as SSB and
CW), no signal at all.

mole

The SI base unit of quantity of
a substance. Symbol is mol. Defined as the amount of substance of a
system which contains as many elementary entities as there are atoms
in 0.012 kilogram [i.e., 12 g] of 12C. Note that
"mole" by itself is meaningless; one must specify the elementary
entities being measured, which may be specific atoms, molecules, or
ions; electrons or other particles; or specified groups of such
particles.

Momentum

Ignoring relativity, Mass
times velocity: p=mv.
Since velocity is a vector
quantity, so also is momentum. Total momentum is a conserved property
in any closed system. Symbol is p. There is no named
SI unit for momentum; its units
are kg⋅m/s. For objects at relativistic speeds, momentum is given
as mvγ. See entry gamma
for details.

The number of deaths, in general or due to a specific cause, in a
population per unit time. Usually represented as a percentage of the
population size. Contrast with morbidity.

MSDS

Material Safety Data Sheet. One of around 500,000 documents
that details the characteristics of a substance sold or used
in the US. Both the OSHA
Hazard Communication (HazCom) Standard and
EPRCA §311 require
employers to have an MSDS for each hazardous chemical in their
facility. Many of the MSDS can be looked up at this web site:
Vermont Safety Information Resources,
Inc. MSDS.

MUF

Maximum Usable Frequency.
The highest radio frequency
that can, under specified conditions, be reliably used for communication
via refraction of the wave by layers of ionized gas in the
ionosphere. MUF depends
on solar activity, especially sunspots: the more activity, usually the
more ionization and the higher the MUF; and on the time of day:
especially at night, absent the sunlight, some of the ionized layers
disappear. On a given day, radio communications may or may not succeed
at the MUF—the optimal operating frequency for a given path
is usually estimated to be around 80% to 90% of the MUF.

Myocardial

Pertaining to the muscle of the heart (the myocardium).

N (symbol)

N is the SI symbol for the
derived unit of force, the
newton. N is also the symbol
for the chemical element nitrogen. N or
ℕ represents the set of all natural numbers.

Na

Na is the chemical symbol for sodium.

Narcosis

A state of drowsiness, stupor, or greatly reduced activity caused by a
chemical or physical agent. Thus sleep deprivation does not count.
Often associated with drugs, it can be caused by a number of substances.

Natural number

One of the "counting numbers," designated N: the
positive integers. If zero is
included, may be designated N0.

In radio usage, a net is a controlled meetup of several individuals,
using a common frequency or set of frequencies. There is a net control
operator who is responsible for being the "traffic cop"; most net
communication is through or with the net control operator.

Neurotoxin

A substance whose primary
toxic effect is on the
central nervous system (CNS).

Neutralize

To make a substance less chemically reactive, or to change the
ambientpH to approximately 7.

newton

The SI derived unit of
force.
Symbol is N; named of course for Isaac Newton. By Newton's formula
F=m⋅a (force equals
mass times
acceleration),
this works out to SI base units of kg⋅m⋅s-2.

NFA

National Fire Academy. Run by
FEMA's US Fire Administration
in Emmitsburg MD.

NFPA

National Fire
Protection Association. An international voluntary organization
formed to promote and improve fire protection and prevention.
Publishes the National Fire Codes, a multi-volume set of
standards, recommended practices and manuals.

NGO

Non-Governmental Organization. Somewhat loosely defined category of
agencies that at least are not associated directly with a govenment
(though may be chartered or partially supported by one). An NGO is also
nearly always a not-for-profit organization. Term was created by the
United Nations (which is a prime example of an NGO) in 1945.

NIMS

National Incident Management System. Developed and managed by
DHS, this is a version of
ICS and
UCS for use at a national
level. As a central part of the NRP,
NIMS provides a consistent nationwide template to enable all
government, private–sector, and nongovernmental organizations
to work together during domestic incidents. For further information, see the
NIMS website
from FEMA, and the
on–line courses on NIMS
offered by the EMI.

Northeastern Illinois Public Service Training Academy. (From their
web
pages: ) "An
intergovernmental agency comprised of municipalities, fire protection
districts, and other organizations located in the Chicago metropolitan
area that have combined energies and resources to create a regional,
state-of-the-art public safety training facility." NIPSTA occupies a
20 acre campus, part of the former Glenview Naval Air Station. Of
personal interest because it was in the NIPSTA Field Training Facility
where ECRV 4711 resided
when it was not in service, and in the NIPSTA Education Center where
many elements of Red Cross training are provided for the Chicago area.

NIST

(US) National Institute of Standards and Technology. Formerly known as
the National Bureau of Standards (NBS, 1901-1988), the successor to the
Office of Standard Weights and Measures, part of the US Treasury
Department (1830-1901). An agency of the US Department of Commerce
that sets standards for US usage of weights and measures, and provides
metrology expertise to the country. A time standard is provided via radio stations
WWV, WWVB and WWVH on various
carrier frequencies, as well
as via phone (1-303-499-7111 in the US) and the internet (using
NTP).

NOAA

US National Oceanic & Atmospheric Administration. Runs
the National Weather Service (NWS), which provides weather
forecasts nationwide, especially through its network of
NOAA Weather Radio
stations for Illinois counties. Co–developer of
ALOHA, since weather
conditions strongly affect the distribution of hazardous materials
in the air.

NOAEL

No Observed Adverse Effect Level. The highest experimental dose for
which no adverse health effects have been documented. Formerly used
by the US EPA to set
RfC and RfD values. Has been
superseded by BMC/BMD
methods.

Noxious

Capable of causing injury, or harmful effects on health. See also
"toxic."

NRC

National Research Council of the National Academy of Sciences.

NRC

National Response Center of the
EPA. Receives reports of
hazardous materials releases.

NRP

National Response Plan. Establishes a comprehensive all-hazards
approach to enhance the ability of the United States to manage
domestic incidents. The plan incorporates best practices and
procedures from incident management disciplines—homeland
security, emergency management, law enforcement, firefighting,
public works, public health, responder and recovery worker health and
safety, emergency medical services, and the private sector—and
integrates them into a unified structure. The NRP is predicated on
NIMS. Together the NRP and
the NIMS provide a nationwide template for various agencies to work
together in preventing or responding to threats and incidents
regardless of cause, size, or complexity.

NRT

US National Response Team. A cooperative effort of the EPA, NOAA, and the Coast Guard. It does not respond
directly to incidents, but (1) distributes information, (2) plans for
emergencies, and (3) trains for emergencies.

NTP

Network Time Protocol. An OSI
layer 7 (application layer) network
protocol Used to
synchronize clocks across a computer network, especially the internet.
Somewhat limited in ultimate
accuracy by network
latency, it still is capable of maintaining time within 10 ms,
even over the internet. On a local network, it is much more accurate.

Nucleotide

Basic chemical components of all living organisms. They form the
polymers of DNA and of
RNA, and perform other
biochemical functions such as energy storage and as components of
enzymes. DNA uses four
nucleotide bases ("nucleobases"):
adenine (symbolized: A),
cytosine (C),
guanine (G), and
thymine (T); RNA substitutes
uracil (U)
for thymine. The sequence of these nucleobases forms the genetic code;
triplets of the nucleobases code for amino acids in proteins. For DNA, A pairs with T and C with
G in its double, helical strands.

A nucleobase linked to a ribose
or deoxyribosesugar on
the sugar's 1' carbon is known as a nucleoside. The four
ribose–based nucleosides corresponding to the above listed
nucleobases are adenosine, cytidine, guanosine and uridine. For DNA,
which uses deoxyribose sugar, prepend "deoxy" to the above names:
deoxyadenosine, deoxycytidine, etc. Also add [deoxy]thymidine in place
of uridine. A nucleotide (note subtle spelling difference) consists of
one of the above nucleosides ester–linked to at least one
phosphate group through
the 5' carbon of the sugar. The RNA and DNA chains of nucleotides
use a single phosphate group to ester link the 3' carbon of one
[deoxy]ribose to the 5' carbon of the next. This leaves an unpaired
carbon at each end of the chain. The RNA and DNA ends are thus called
the 3' end and the 5' end. For an example of the structure
of a representative RNA nucleotide (adenosine monophosphate), see entry
ATP.

NVOAD

National
Voluntary Organizations Active in Disaster.
Organization of
American national disaster relief agencies with the goal of
fostering more effective service to people affected by disaster.
The key NVOAD principles are cooperation, coordination,
communication, education, mitigation, convening mechanisms, and
outreach. There are national members, and also state
VOADs.

Symbol Ω (Greek capital omega); named for Georg Simon Ohm. Measure
of the opposition to current flow in an electrical circuit.
The ohm is an SI derived unit,
equal to a volt
per ampere, a
watt per squared
ampere, or in SI basic units:
kg⋅m2⋅s-3⋅A-2. For details,
see resistance,
reactance, and
impedance, all of which
are measured in ohms.

Oligosaccharide

A polymer of a few simple sugars,
typically three to nine, formed by chemical condensation.

Order of Magnitude

As used here, and in common usage, an approximate factor of 10 difference
between two numbers. If two numbers differ by one order of magnitude, one
number is about ten times larger than the other. If they differ by two
orders of magnitude, they differ by a factor of about 100 (102),
and so on for higher integer
powers of 10.

Organic chemicals/compounds

Naturally occurring (animal– or plant–produced) or
synthetic substances containing carbon, plus some combination of
hydrogen, oxygen, and nitrogen. Phosphorus and sulfur are also
often part of an organic compound. More than 10 million have
been identified. The opposite is "inorganic." For examples, see
the entries for ALA,
n–butyl acetate,
DMSA,
DTPA and
EDTA. Since both
DNA and
RNA are organic compounds, the
number of distinct organic compounds in nature must be in the trillions.
The term "organic food" is little more than a marketing gimmick. The
only non-organic food type substance I can think of is table salt (NaCl),
and I've even seen examples of that called "organic."

ORM

Other Regulated Material. A DOT
classification of some hazardous materials for labeling during
transportation.

OSH Act

US Occupational Safety and Health Act of 1970,
29 CFR 1910 et seq.
Administered by OSHA for firms with ten or more employees. The act
established the Hazard Communication
(HazCom) Rule.

The Open Systems Interconnection model is the model that is most often
used to describe the elements of a communications system such as (in
particular) a computer network. It partitions the functions of such a
system into seven layers. Here are brief, and necessarily incomplete,
descriptions of each of these layers:

Level 2, Data Link Layer: allows for transfer of data between
directly–connected devices. Sometimes loosely called the
MAC (media access control) layer, from one of its sublayers. MAC
addresses are built into devices and are unique.

Abbreviated "OX". The DOT
narrowly defines an oxidizer or oxidizing material as a substance that
readily yields oxygen to cause or enhance the combustion [burning] of
other materials. Some oxidizers, such as chlorine, act only when exposed
to other substances. The definition of oxidizer in chemistry is broader.

Ozone

A form of oxygen molecule,
O3, that is relatively unstable, particularly at higher
pressures and temperatures. See the diagram on the right. It is formed
when a free oxygen atom reacts with an ordinary oxygen molecule,
O2. The free oxygen atom is formed by high energy
electromagnetic radiation
from sunlight, such as ultraviolet
light of wavelength <240 nm or x-rays, splitting O2.
In the low–density upper atmosphere ozone can persist for several
hours to a day. Often naturally destroyed by the same oxygen atoms that
formed it, ozone is also vulnerable to atmospheric pollutants, notably
chlorofluorocarbons. Ozone is much more reactive, even explosively so,
than molecular oxygen, and has a sharp odor. Ozone is valuable to us,
since it effectively blocks some of the shorter, more dangerous
wavelengths of ultraviolet light longer than about 200 nm that
are not blocked by atmospheric oxygen and nitrogen.

P (symbol)

P is used as the symbol in electronics formulas representing electrical
power. P is also the symbol for
the chemical element phosphorus. Lower-case bold p is the
symbol in physics for momentum.

Pandemic

Noun and adjective, referring to an occurrence of an
infectiousdisease in a large geographic
region, possibly worldwide, for a limited period of time. Compare to
epidemic and
endemic.

pascal

Symbol Pa; named for Blaise Pascal. The
SI derived unit of pressure, equal
to one newton of force per
square meter. In SI base units
this works out to kg⋅m-1⋅s-2. Standard
earth atmospheric pressure is taken to be 101 325 Pa .

Portable Document Format. Developed by Adobe® Systems,
Incorporated, it is a widely used and supported form for distributing
documents electronically. Some of the information available from this
website is in PDF files. For more information, see the
Adobe PDF webpage.

PEL

Permissible Exposure Limit. The maximum or
TWA amount or
concentration of a
substance to which a worker may be exposed, under
OSHA regulations. About 470
substances have OSHA PEL's. Exposure can be by inhalation, or by
absorbtion through the skin
or eyes.

Roughly, a measure of the acidity or alkalinity of a substance. Pure
water at 25 ℃ is considered neutral, with a pH close to 7.0.
Substances with pH much below 7 are acid; the lower the value, the
more acid. Those much above 7 are alkaline; the higher the value, the
more alkaline. A commonly used formal chemical definition is
−log10[H+], where the brackets
indicate concentration
of hydrogen ions (H+) in
moles per
liter. But even this is an
approximation in some cases to what would be measured.

Phase (of matter)

A physically distinctive form of a substance. Examples are solid, liquid,
gas, and plasma.

Phase angle

In an alternating current
electrical circuit, represents the difference in angular degrees between
the peaks of voltage and current (in a direct current circuit these would be the same).
The value ranges ±90°. In a primarily inductive circuit, voltage
peaks lead the current peaks; this is considered a positive phase angle.
A primarily capacitive circuit has voltage peaks lagging the current ones
and a negative phase angle. See headings
reactance and
impedance for more
information.

PHC

Principal Hazardous Constituent. In a mixture, the component that has
the greatest potential risk.

Inorganic phosphates are just salts of phosphoric acid: (HO)3P=O.
Organic phosphates, which largely are the ones referenced in this glossary,
are esters of that acid. See the
entry for ATP for an example of how
organic phosphates link up. An organic monophosphate group looks like
(OH)2O=P-, where the right-most bond of the phosphorus is to the
ester link oxygen.

Photophobia

Intolerance to light. Discomfort or pain on exposure to light. Not a
"phobia" in the usual sense of "fear." Many possible causes, including
eye defects, drug reactions, and diseases.

Private Line. A Motorola trade name, often used for the proper term:
CTCSS.

Plasma

A state of matter in which
molecular bonds become dissociated, and atoms become ionized. Electrons
from the atoms are independently part of the plasma. Plasma is the
most common form for matter in the universe.

Plume

A volume of a substance that moves from its source to places farther
away from the source. Plumes can be described by the volume of air
or water they occupy and the direction they move. For example, a plume
can be a column of smoke from a chimney or a substance moving with
groundwater.

Pneumonia

A disease characterized by
inflammation of and accumulation of fluids in the lungs. Although
usually thought of as an infectious disease, pneumonia can also be
caused by physical and chemical irritants, or by inhaled fluids.

PNG

Portable Network Graphics, a file format for the lossless, portable,
well-compressed storage of raster images. PNG provides a patent-free
replacement for GIF and can also replace many common uses of TIFF.
Graphic images on this web site are largely PNG format.

Towards the rear end of an organism. For many vertebrates, also known as
"caudal" (tail). Opposite of anterior.

Pound

One of the many reasons for avoiding use of units outside of
SI ones. For historical reasons,
in common use "pound" refers to a unit of force (weight). In this case, the unit of mass
is typically the "slug." "Pound" can also be used as a unit of
mass in another system of units.
Engineers stuck with this (mostly in the US), clumsily distinguishing
pounds–force, symbol lbf from pounds–mass,
symbol lbm. The latter, in the form of the "international
avoirdupois pound" is by definition 0.453 592 37 kg.
So it all ties back to SI in any case. I'll stick with N and kg.

Power

In physics, power is the rate of performing work or using
energy per unit
time. The
SI derived unit of power is the
watt.

PPE

Personal Protective Equipment. Devices or clothing used to help
isolate a person from direct exposure to hazardous materials.

ppm / ppb

Designates a concentration expressed in
Parts Per Million or in Parts Per Billion (thousand
million). Usually this is the ratio by
mass (loosely speaking,
"weight"), often
designated by the suffix "w/w,"
but it is occasionally by volume, designated
"v/v".

Precision

The degree to which repeated measurements of a quantity show the same
value. Also known as repeatability. Contrast with accuracy and resolution.

Prevalence

The number of existing
disease cases in a
defined at-risk population during a specific time period or more
usually as the fraction or the percentage of that population with the
disease (prevalence rate). A measure of
morbidity. [Contrast with
incidence].

Prime (number)

A prime number is a natural
number greater than one which is not exactly divisible by any natural
number other than itself and one. The only even prime is 2, since all
other even numbers are divisible by 2. Non-prime natural numbers are known
as "composite." The count of prime numbers less than or equal to n is
designated by the function π(n); no exact formula exists for this
function, but the prime number theorem gives it as approximately
n/ln(n). Euclid (book IX, proposition 20) gave a proof that there is no
largest prime; hence there is a (countably) infinite number of them.

Proper Time

In special relativity, the time interval local to a moving entity,
denoted dτ, as distinguished from coordinate time, dt. The ratio of these intervals
(dt/dτ) is given by the Lorentz
factor (γ). Proper time interval Δτ is given as
(Δ²t−[Δ²x+Δ²y+Δ²z]/c²)½.

Protein

Also known as polypeptides, proteins are complex
organic molecules, composed
of amino acid residues, joined
at a carboxyl group of one amino acid to an amino group of another by
chemical condensation.
Proteins form in straight or branching chains of the amino acids. In
organisms, proteins are ubiquitous. They form structural elements, and as
enzymes, catalyze most biochemical reactions. Also in
organisms, proteins are formed via templates of RNA derived from DNA sequences.

Protocol

In computer networking terms, a protocol is set of rules which is used
by computers to connect, communicate, and transfer data with each other
across a network. These include lower level protocols such as
DSL and
ISDN [OSI layer 2],
TCP/IP [OSI layers 4/3], and
higher level [usually OSI layer 7] ones such as
DHCP,
SNMP,
NTP,
HTTP, and
FTP.

Proximal

Located closest (or closer) to the point of origin or attachment.
Relatively close to the mass of the body. The point of reference may have
to be specified in particular cases. Synonym of "central." Opposite of
"peripheral" or distal.

PRP

Potentially Responsible Party. A company, government, or person legally
responsible for cleaning up the pollution at a hazardous waste site
under Superfund.
There may be more than one PRP for a particular site.

PSAP

Public Safety Answering/Access
Point. Often known
in the US as a "9-1-1 Center." The location and associated real phone
number that is called to report emergency (e.g., police, fire, weather)
situations, when a phone company customer "dials" the number 911. The
local telephone company's telephony switch is responsible for translating
"911" into the actual number of the PSAP.

PSTN

Public Switched Telephone Network: all the electronic,
fiber optic, RF, satellite,
electromechanical, etc. components that together allow voice and data
connections between publicly accessible telephones around the world.
Details of PSTN operation differ from place to place.

Public health advisory

A statement made by
ATSDR to
EPA or a state regulatory
agency that a release of hazardous substances poses an immediate threat
to human health. The advisory includes recommended measures to reduce
exposure and reduce the threat to human health.

A class of aromaticorganic chemical
compounds with a double ring: a pyrimidine ring with a second, 5-atom ring sharing
the carbon atoms of pyrimidine at locations 4 and 5, and with -NH-CH=N-
connecting those. Purines are very common in nature. In particular,
DNA nucleobases
adenine and
guanine are purines. Other
well–known purines are caffeine and uric acid.

A substance that can spontaneously burn when exposed to air. It is
not only atmospheric oxygen that ignites them: they may also burn more
intensely if a
CO2
fire extinguisher is used on them, or if they are exposed to water
(liquid or vapor). Not a household item, but this type of material is
often used in chemical manufacturing.

Q (symbol)

Q or ℚ represents the set of all
rational numbers. In physics,
Q represents heat energy.

Q (factor)

Originally indicating the "quality" of a resonant circuit, or in general
any oscillator, it is today nearly always just referred to as "Q" or the
"Q factor." Q is a strictly positive dimensionless quantity. In
amateur radio usage, Q most
commonly refers to how "sharp" or "tight" an electrical circuit's frequency
response is: a high Q circuit has narrow bandwidth and high
selectivity. One definition
for Q is the ratio of the resonant (peak) frequency to the
half–peak–power (-3 dB)
bandwidth (in the same units). Q can also be computed as the ratio of the
circuit's reactance to its
resistance.

High Q is not always desirable (or "high quality"). For example, one might
well wish a general–use antenna to have low Q, and a correspondingly
wide bandwidth. For further details on this subject, including applications
of Q in acoustics, mechanics and other non-electronic fields, see the
Wikipedia article on the subject.

Q signals

Q signals are a standardized set of three-letter codes; "Q" is the first
letter of each code. Originally developed for telegraphy, as shortcuts in Morse
code, they are often used for brevity in informal and casual amateur radio voice transmissions. They are, however,
deprecated when used outside that scope, such as in emergency communications,
since they are in effect "jargon" and likely not to be understood by a general
population. For a list of Q signals commonly used in amateur radio, see this
Wikipedia table.

Quaternion (number)

×

1

i

j

k

1

1

i

j

k

i

i

−1

k

−j

j

j

−k

−1

i

k

k

j

−i

−1

An extension of complex numbers,
also known as Hamiltonian
numbers, whence the symbols H amd ℍ for them.
Whereas complex numbers extend real
numbers to represent 2-dimensional concepts effectively (see in particular
the entry for impedance),
the quaternions are especially useful in describing rotations in 3-dimensional
space. Unlike reals and complex numbers, quaternions are not
commutative. In addition to
i as found in complex numbers, there are multipliers j and
k. The relationships between these are as shown in the table on the
right. Note that i⋅j⋅k = i² = j²
= k² = −1. Note also how multiplication of quaternions is not
commutative: i⋅j=k, but j⋅i=−k.
Just as a complex number can be expressed as a+bi, a and b real, so
a quaternion can be written as a+bi+cj+dk, with
a, b, c and d real. The first element is known as its pure real scalar part,
and the remainder as its pure imaginary (3-)vector part.

Quarantine

The temporary segregation from the general population, whether voluntary or
compulsory, of persons, other animals, or physical objects who or which may
have been exposed to a contagiousdisease, to prevent further
spread of the disease. The term originated from Venetian Italian, indicating
a 40-day period for the separation, but in practice the period of separation
can be quite variable. In strict usage, "quarantine" is distinguished from
"isolation," in that the ones
quarantined may or may not be or become ill from the disease.

R (symbol)

R is used as the symbol in electronics formulas representing electrical
resistance.
R or ℝ represents the set of all
real numbers.

RACES

Radio Amateur Civil Emergency Service. Volunteer organization of
amateur radio operators
organized under a sponsoring government agency, typically an
ESDA or an
EMA. RACES members are prepared,
trained and equipped to assist with communications in an emergency, when
activated by the sponsoring agency. See also ARES.

Radio

As used in this glossary, the adjective "radio" refers generally to any
electromagnetic radiation of
frequency less than that of
light that is deliberately used to transmit information. As a noun, it thus
includes (broadcast) radio and television receivers, RFID tags, satellite communications, radar,
cell phones, garage door openers,
Wi-Fi,
GPS receivers, remote car starters,
and so on. The upper radio frequency limit is around 300 GHz, at the
extreme lower edge of infrared light.
The lower limit is in the ELF range. See the entry for
Radio Frequency.

Rational (number)

A number that can be expressed as a fraction; that is as a ratio
of two integers. Designated
Q. Rational numbers constitute an infinitely
countable set of numbers.
Real numbers that are not
rational are called "irrational," and since real numbers are uncountable,
"almost all" of them are irrational.

Raster

A raster image is one that is stored as a dot matrix, a generally rectangular grid of colored
points. Distinguished from a vector
graphic image. Raster images are generally only usable within a limited
range of sizes. They are, however, best suited to easy image display; thus
html with its "img" tag assumes a
raster image file format such as png, jpeg, gif or the like.

RCRA

The Resource Conservation and Recovery Act of 1976. Authorized the
EPA to control hazardous waste
from "cradle to grave," including its generation, transportation,
treatment, storage, and disposal. The corresponding EPA regulations are in
40 CFR 240–299.
RCRA also created a framework for management of non–hazardous
wastes. In 1984, the Hazardous and Solid Waste Amendments (HSWA) were
added to RCRA. This requires phasing out of landfill disposal of
hazardous waste.

Reactance

(Electrical) reactance, measured in ohms, with symbol X, is the imaginary number component of
impedance in an electrical
circuit. It appears in two complementary forms:
inductive, symbol
XL=2πfL, and
capacitive, symbol
XC=1/(2πfC), where f is
frequncy in hertz,
L is inductance in
henries and C is
capacitance in
farads. These reactances are
due to presence in the circuit of inductance and capacitance, respectively.
XL is taken to have values of multiples of
+i (or +j if\ you're an EE), and
XC has values of multiples
of -i; thus for a given ACfrequency, it is possible for
inductive and capacitive impedance to cancel each other out. The frequency
at which this occurs is known as the "resonant" frequency of the circuit.
In general, X is frequency dependent.

Real (number)

A number that represents any point on a number line, including for example
one represented by any arbitrary string of decimal digits. Designated
R. If distinguished from a rational number, it is called "irrational,"
designated I, and is represented by an unending,
non-repeating string of digits. Real numbers constitute an (infinitely)
uncountable set. Compare the
computer use of the term.

Of a medical condition, one that occurs or appears repeatedly or
periodically, as opposed to acute
or chronic conditions.

Resistance

(Electrical) resistance, measured in ohms, with symbol R, is the real
number component of impedance.
It is the only effective component in a DC
circuit; or in an AC circuit without
inductors or
capacitors, real or effective.

Resolution

The smallest change in a physical quantity that results in a measurable
change. Particularly noticeable on a measuring device with a digital
readout that does not allow for interpolation. For that, the resolution
is limited by the last displayed digit. Contrast with
accuracy and
precision.

RF

Radio Frequency. This is a rate of oscillation, typically of
electromagnetic radiation signals or
their associated alternating currents, that can range from a few
hertz (so-called "ELF": Extremely Low
Frequency signals) to hundreds of gigahertz (short
of frequencies that would be otherwise called
"infrared light"). The ITU has definitions for each radio frequency band;
each band is an order of magnitude
higher in frequency and shorter in wavelength. Here is the ITU list, showing
the band code and designation, followed by the frequency range, the wavelength
range, and my notes on any other identifying information:

Reference Concentration and
Reference Dose. US EPA estimates, with uncertainty or safety factors built
in, of the daily lifetime environmental concentration or dose of a substance
that is unlikely to cause harm in humans. The US EPA uses BMD techniques to determine these values. See also
ARfD, and
ADI.

RFID

Radio Frequency IDentification. Term applies to a variety of passive or
active devices that contain electronically coded identification information,
and which respond to radio signals
that request that identification information. RFID tags are used to track
packages, identify pets, and for automated toll collection on the road, among
many such applications.

Ribose

Pentose
(formula C5H10O5) sugar that
inter alia
is a central component of RNA and
DNA. Structures of the RNA and DNA
(deoxyribose) versions are shown at the right. Note that the difference is on
the 2' carbon: deoxyribose has a hydrogen in place of a hydroxyl (-OH)
group (hence one fewer oxygen: "deoxy"). In an RNA or DNA molecule, the ribose
is ester linked to one of the
nucleobases at the ribose's
1' carbon; the ribose groups are themselves connected into the long RNA
and DNA chains via ester links at their 3' and 5' carbons to a
phosphate group.

Riemann hypothesis

Has nothing much to do with anything else in this glossary, but is fascinating
as one of the few unsolved mathematical ideas. It says that the non-trivial roots
of ζ(s) all have real part ½. Widely assumed to be true in proving
other mathematical hypotheses, particularly with regard to prime number distribution, it has resisted proof itself
for a century and a half.

Ring

A mathematical (algebraic) structure. It consists of a
commutative (aka abelian)
group plus a second binary operator
that may be applied to any pair of elements of the set. An example ring is
(as with the group) the set of integers (ℤ) and addition operator, plus
also the multiplication operator. The second operator must have four properties.
(1) Closure: the result of applying the second operator to any two set
elements must also be in the set. (2) Associative: as with the group this
means that when there are two or more operators in a row, the order in which
the operators are applied is irrelevant. The order of the elements themselves
is relevant unless like the example, the ring is also commutative.
(3) Distributive: readily represented by the example ring: ∀ x,y,z
∈ ℤ, x⋅(y+z) = (y+z)⋅x = x⋅y+x⋅z.
Note that it is the second (new) operator that is distributive over the group
operator: x+(y⋅z) ≠ (x+y)⋅(x+z). (4) Identity: the second operator,
like the first, has an "identity" element, such that applying that element to
any element of the set via that operator leaves that set element unchanged.
In the example ring, the multiplicative identity element is the number one.

Ribonucleic Acid. Used in all living organisms as templates for making
proteins in cells, in regulating
gene expression, as
catalysts for cellular
reactions and as components with protein of other catalysts, among many
functions. Its structure is a (usually) single-stranded polymer of
nucleotides. In organisms,
RNA is transcribed from sequences of the nucleotides in DNA molecules. See ATP for an example of the structure of an RNA
nucleotide (adenosine monophosphate). Other RNA nucleotides commonly
use—instead of adenine—
cytosine,
guanine or
uracil.

RQ

Reportable Quantity. Any release of one or more of the roughly 800
CERCLA or 360
EPCRA hazardous substances
that equals or exceeds this quantity (RQ) in any 24–hour period
must be reported to the NRC
at the EPA. The RQs are
adjusted to one of five levels: 1, 10, 100, 1000, or 5000 pounds.
EPA bases adjustments to the RQs on the intrinsic characteristics of
each hazardous substance, such as the aquatic
toxicity,
acute and
chronic toxicity,
ignitability, reactivity, and potential
carcinogenicity.
An RQ value is established for each of these characteristics of a
hazardous substance, with the most stringent RQ value (i.e., the lowest
quantity) becoming the final RQ or reporting trigger for that hazardous
substance.

RSPA

The research functions of the Research and Special Programs
Administration of DOT
were replaced in 2005 by RITA.
The pipeline safety function was moved to
PHMSA. The
OET became part of the office
of the Secretary.

RTECS

Registry of Toxic Effects of Chemical Substances, published by
NIOSH. Has
toxicity data on numerous
materials, with references to the studies that generated the data.

S (symbol)

S is the symbol for the SI unit of
conductance (the inverse of resistance) known as the siemens, named for Ernst
Werner von Siemens. Units of the Siemens are Ω-1, or A/V.
In physics, S represents entropy.
S is also the symbol for chemical element sulfur.

SARA

Superfund Amendments
& Reauthorization Act of 1986. Title III of SARA is
EPCRA, under the provisions
of which the LEPC was
organized.

Saturated

Of an organic chemical
compound, means that the carbon atoms are all linked to each other by
single bonds. If there are any double or triple bonds between carbon
atoms, the compound is described as "unsaturated." A
fat is saturated or unsaturated
depending on the links within the constituent fatty acids.

Scalar

A "simple" numeric value, invariant under coordinate system rotation.
Also (rather whimsically) decribable as a zero-rank tensor.

second [time]

The SI base unit of
time interval. Symbol is s.
Defined as the duration of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the Cs 133 atom at
0 K, located at a fixed
position on the gravitational equipotential of the earth's geoid at
mean sea level. Which I'll admit is as clear as mud to non geeks. Sorry
folks, but that's the way it is. The bits about "fixed position" and
"sea level" are there to allow for effects of relativity. Given that
the earth's orbit around the sun and the moon's about the earth are
elliptical, and thus the sun's and moon's gravitational fields at the
earth vary, I'm surprised the definition doesn't also specify the time
of month and year. Also, what happens if sea level rises? Just asking.

Selectivity

This definition applies to the term's use in radio receiver technology. Selectivity
measures how well a radio receiver responds only to the frequency to which it is tuned, rejecting nearby
("adjacent channel") radio signals. Tuned circuits with a high
Q factor will tend to be more
selective, though there are other means of increasing selectivity.

Sensitivity

Sensitivity of a test, also known as the recall rate, measures the
proportion of actual positives which are correctly identified as such
by the test. Corresponds to a type II or β probability statistical
error (false negative: the test incorrectly retains a null hypothesis),
a significantly large value of which would indicate poor sensitivity.
Contrast with
specificity. Consider a
drug-testing model: a highly sensitive test will detect nearly all who
have used the drug being tested for; it will have a low β error
rate.

Sensu

Latin ablative singular of
sensus [4]: "in the
sense [meaning] of." Used with an adjective indicating the intended
breadth of meaning. For example,
"sensu stricto" =
"in the limited/restricted sense" means what "literally" is often
thought to mean literally (though the Oxford English Dictionary also
recognizes an emphatic sense of that word).
"Sensu lato" means
"in the broad sense" or perhaps "loosely speaking."
"Sensu latiore,"
"in the broader sense" means roughly "whatever you care to make of it."

State Emergency Response Commission. A general term used to
designate the state agency responsible under
EPCRA for organizing the
LEPC and collecting hazardous
materials information. In Illinois, the SERC is
IEMA.

SHF

Super High Frequency radio waves,
specifically those with frequencies of 3-30 GHz, or wavelengths of
10-100 mm (around an inch).

The SI symbols listed in this glossary are just that: symbols, not
abbreviations. Capitalization of the symbols is significant, they are not
pluralized, and they are never followed by a period (hardly ever; unless, of
course, they occur at the end of a sentence). If you should write, say, "Ms"
for "meters," you would have actually written the symbol for megasecond. I
often see "Kgs" (instead of kg) for kilograms; this actually represents a
kelvin⋅gram⋅second, whatever that might be. Whatever … it's
simply wrong.

SIP

Shelter In Place. Remaining in a location where hazardous
materials are in the environment, while taking precautions
to minimize exposure to those materials.

SIRT

[IL] State Interagency Response Team.

SNMP

Simple Network Management Protocol. An OSI
level 7 (application layer) computer network protocol that provides
monitoring and management of IP
network devices, especially routers, switches, servers, printers and
the like. Can also be used at the workstation level, but those are more
commonly handled by DHCP.

Solvent / solute / solution / soluble

A solvent is a substance that dissolves another substance or substances
to form a solution (a homogeneous mixture). The solvent is the component in the solution
that is present in the largest amount, or is the one that determines the
state of matter of the solution.
Solvents are often, but not always, liquids. They can also be gases or
solids. The material dissolved in the solvent is called the "solute."
Together, the solvent and solute comprise the "solution." A solute
substance that readily dissolves in a particular solvent is said to be
"soluble" in that solvent. For example, a substance that dissolves in
water is said to be "soluble in water," or more simply "water soluble."

Specificity

Specificity of a test measures the proportion of negatives which are
correctly identified by the test. Corresponds to a type I or α
probability statistical error (false positive: the test incorrectly
rejects a null hypothesis), a significantly large value of which would
indicate poor specificity. Contrast with
sensitivity. Consider a
drug-testing model: a highly specific test will rarely give a positive
result for a non-user; it will have a low α error rate.

SPEGL

Short–term Public Emergency Guidance Level. An acceptable
concentration of a
substance for unpredicted, single, short–term exposure of the
general public to that substance in emergencies. Developed by National
Academy of Sciences, NRC.

SSB

Single Side Band radio signal
modulation. A pared-down
form of AM, which for efficiency
and minimal bandwidth, transmits only one "side" (either upper or lower)
of the full AM signal, and which usually—always in
amateur radio
technique—suppresses the carrier as well.
Downside of SSB is that lacking a carrier reference, receiving the signal
is bit more fussy. Also one has to be aware which of the sides is being
used. Common practice conventions denote this last factor.

SSID

As used here, means "sub-station Identifier"; the same acronym is also
used in networking. A sub-station ID for an amateur radio call sign is a number from 1 to 15
appended after a hyphen to the base call sign. It indicates a separate
transmitter used concurrently with another under the base call sign to
distinguish it. For example, I may be operating a voice or Morse code
transmission on one frequency as NE9ET while sending APRS packets reporting my status and location on
another (typically 144.390 MHz in the US) as NE9ET-9.

Staging area

The location designated by the
ICS Liaison Officer or
Incident Commander where personnel and equipment not immediately
needed for an emergency response are organized and kept ready for
use.

Starch

A mostly insoluble polysaccharide (many sugar unit) organic chemical compound made up of
glucose subunits bonded by
chemical condensation.
There are two, related components of starch, both deriving from glucose:
amylose (helical) and amylopectin (branched). Both are
hydrolysed by
amylase. Starch serves as a
compact food reserve in plants, but is also usable as food by most animals.
Humans have also found uses for starch in cooking and in
manufacturing—particularly of paper and textiles.

State of matter

For our purposes, one of solid, liquid, gas or
plasma. Most substances
can exist, depending on temperature and pressure, in any one or a
combination of these states.

STEL

Short–Term Exposure Limit. The
concentration of a
substance to which people can be exposed continuously for a "short"
period of time without suffering from (a) irritation, (b)
chronic or irreversible
tissue damage, or (c)
narcosis of sufficient
degree to increase the likelihood of accidental injury or to impair
self–rescue.

Stereoisomer

Stereoisomers are chemicals with the same molecular formula (isomers) and
sequence of atoms, differing only in the 3-dimensional orientation of the
atoms. Contrasted with structural isomers, such as butane and isobutane
(2-methylpropane). Biological stereoisomers are usually enantiomers, that is mirror images of each other.
In nature, usually only one of these forms is biologically active.

STP

No, not the automotive petroleum products manufacturer or any of several
other possible interpretations. Here, it has the meaning as in chemistry
and physics of "Standard Temperature and Pressure"—the conditions
under which physical properties are commonly measured. Defined as
0 Â°C temperature and
101 325 Pa
atmospheric pressure.

Strain

A deformation of a solid object due to an applied force. The force is usually referred to
technically as a "stress," although in common usage these two terms
are often equated.

Sublime

To change state directly
from a solid to gas, without passing through a liquid phase. The opposite of deposition.

Sugar

Generally, a short-chain, water soluble, sweet carbohydrate, often found in foods. Also used
to mean specifically "table sugar" or sucrose. Sucrose is made up of
two simple sugars, fructose and glucose, and so is called a disaccharide.
Lactose (milk sugar, which many adults cannot digest) is another
disaccharide, made up of galactose and glucose. The sugar
ribose is a component of the
backbone of RNA; and the similar
deoxyribose (less one oxygen atom, as its name implies) is similarly a
component of DNA. See also
starch and
cellulose.

Superfund

Set up by the US Congress to fund remediation of hazardous waste
conditions. For connections to
LEPC, see under headings
CERCLA and
SARA.

SWR

Standing Wave Ratio. Also known as Voltage Standing Wave Ratio (VSWR).
It is the ratio of the amplitude (in
volts, for an electronic
system) of the maximum in a standing wave to an adjacent minimum within
an electrical conductor. For the case where there is no standing wave,
the maximum equals the minimum, and SWR=1. In any other case, SWR>1.
For the best impedance
match and effective transfer of electrical
power in a system, one wants
the SWR to be as close as possible to 1. The standing wave itself is
created by the interference of the original (forward) signal in the
conductor with a reflected one from an impedance mismatch. Since
impedance is frequency
dependent, so is SWR.

Symptom

A departure from normal body function observed by a patient, which
is a sign of disease or
abnormality. Note that results of medical tests (e.g., a blood test
for diabetes) are not considered symptoms but signs or indications of
these conditions, since the test result would not be directly noted by
the patient. A medical condition which results in symptoms is called
symptomatic, otherwise it is asymptomatic (the patient is not aware of
the condition until it is diagnosed through medical tests).

Synergistic

A biologic response to multiple substances where one substance
increases the effect of another substance. The combined net effect of
the substances acting together is greater than the sum of the effects
of the substances acting by themselves [compare
additive effect and
antagonistic effect].

Internet Protocol Suite (commonly known as TCP/IP) is the set of
communications
protocols used by the
Internet and similar networks. It is named from the two most important
protocols in it: the [OSI
layer 4 = transport layer Transmission Control Protocol (TCP) and the
OSI layer 3 = network layer Internet Protocol (IP). The address used by
IP is known as an "IP address," which corresponds for example to an
Internet domain name. The TCP address is known as a "port," which
corresponds to an OSI application layer protocol such as http or ftp.
The combination of an IP address and a port is known as a "socket."

A mathematical object that extends the concept of a vector. A tensor in an m-dimensional space can
have an arbitrary integer number of indices (n≥0); it then has
mn conponents, and is known as an n-th rank
tensor. If n=0 (one component), it is a zeroth-rank tensor, also known as
a scalar value. For n=1, it is
an ordinary vector. If n=2, it us usually called a matrix. So the term tensor is typically reserved
for those with n≥3. Notation of a tensor A looks like
Aijk ...λμν ....
The lower indices (i,j,k etc.) are known as "covariant" indices, and the
upper (here Greek) ones as "contravariant" indices.

Teratogen

A substance that causes defects in development between conception
and birth. A teratogen is a substance that causes a structural or
functional birth defect.

Thiol

An organic chemical compound
which contains one or more sulfhydryl (aka thiol) groups. A sulfhydryl
group is -SH, which is analogous to the hydroxyl -OH group of an
alcohol. For an example, see
entry DMSA. Thiols are often
referred to by an older designation as "mercaptans" from a Latin phrase
meaning "capturing mercury." As with DMSA, binding to heavy metals such
as mercury is a common use for thiols. As to the odor of thiols, suffice
it to say that skunk spray consists mostly of low molecular weight
thiols.

Thymine

One of the pyrimidine nucleobases in the
nucleotides of
DNA, whose structure is shown
on the right. In RNA,
uracil is used instead. The
corresponding nucleoside to thymine is [deoxy]thymidine, for which the
RNA equivalent is uridine.

Tier II Report

The Emergency and Hazardous Chemical Inventory form that must
be submitted annually under
EPCRA regulations (§312)
by any facility that has on hand substantial quantities—as
defined by the EPA —
of hazardous substances. The form lists the substances and quantities,
and provides employee contact information. Copies of this form go to
the LEPC, the
SERC and the local fire
department. A Windows program, tier2submit.exe, allows this report to
be created easily.

TIH

Toxic by inhalation. Describes a gaseous material that is toxic when
breathed. Some water-reactive
materials (WRM) that are TIH produce additional TIH substances when
exposed to water (e.g. BrFl3,
SOCl2).

Time

Where (when) do I start? Many large books have been written to explain
time; this is no place for an epitome of them. So to start, I observe
that SI measures time intervals in
seconds. Humans use a variety
of other units also: minutes, hours, days, weeks, months, centuries, etc.
[But not light years or parsecs]. There is no standard clock, however
(see below). Even on Earth we have dozens of time zones, though
UTC has pride of place among them.

Newton (wrongly) supposed that time was a universal constant. Einstein's
special relativity showed us that elapsed time depends on one's path in
spacetime. Fortunately and in practice, we and most of our artifacts do take
much the same path. But not all. GPS
satellites, with their high precision atomic clocks, go somewhat faster
than normal, and also travel in a weaker gravitational field. So their
clocks differ from ours in small but significant amounts.

In special relativity, time is just another coordinate in spacetime, making
time interchangeable with space coordinates. Two observers will likely not
agree on what events (as defined by all four coordinates)
are simultaneous. For events that are not causally connected—that is
ones far enough distant from each other that information at the speed of
light could not pass between them—the observers may even differ on
their order of occurrence.

The only constant in special relativity is the spacetime
interval (Δs) between the events, defined as
Δ2s = Δ2x + Δ2y +
Δ2z − c2⋅Δ2t, with
dimensions of length. This formula, by the way, with positive values for
spatial and negative for time values is known as the "space-like convention"
with a (−+++) metric, in which the first sign is for time. The reverse
convention, with positive time and metric (+−−−) is
equivalent, but not discussed here. (Note that in the space-like convention,
ordinary causally connected events—in which the time component is
larger than the spatial distance—have Δ2s<0, and
thus imaginary number interval
lengths.)

I'll conclude this grossly oversimplified explanation—for one thing,
I've assumed flat (Euclidean) space unaffected by general relativity—by
quoting someone, maybe J A Wheeler and maybe Woody Allen, as "Time is
nature's way of keeping everything from happening at once." Hard to beat that.

Tissue

In biology, a collection of cells, not necessarily identical, that
together perform a specific function in an organism. Tissues are
intermediate in level of organization between cells and organs.

TLV®

Threshold Limit Value. The
ACGIH guideline for the
atmospheric
concentration of
a substance to which nearly all U.S. workers can be exposed day
after day without adverse effect. There are more than 700 of these.

TMDL

Total Maximum Daily Load. The largest amount of a substance that
may be added to a waterway in one day under the provisions of the
National Clean Water Act. This value is determined by the state,
with oversight by the EPA.

ton (tonne)

Apart from metaphorical use to mean "a lot" this is a unit of
measure that is seriously ambiguous. The simplest case is that of the
"metric ton" (often spelled "tonne" to disambiguate it) which is a
mass of
1000 kg = 1 Mg. Note that
this ton is "metric" but is not SI.
The first problem is that, in addition to mass, the term "ton" can be a
measure of weight, volume,
even energy (as in atomic
bombs) or power (as in
refrigeration). We stick to mass (and related weight) here.

Next, in the US and Canada a ton of weight is taken to be 2000 pounds
(also known as a "short ton"). In the UK it is 2240 pounds (a "long ton"
= 160 stone). Then there was once the "ton longweight" at 2400 pounds.
Note that the metric ton can be taken to be approximately 2205 pounds;
but it is not strictly comparable, since "pound" is a unit of weight, and
thus in principle varies with gravity; and the metric ton is an invariant
unit of mass. The ton ambiguity problem is one of the many reasons I stick
to SI units whenever possible.

Toxic[ity]/Toxin

Toxic means capable of causing harmful effects to living organisms
under certain circumstances of exposure. Roughly equivalent to
"poisonous" or
"venomous." Toxicity is the
degree to which a substance is toxic. A toxic substance is often called a
"toxin" (poison or venom). A substance is considered to be a toxin if
there is evidence that it is a health hazard at specified
doses, especially if it is
listed in the RTECS. Note that
the term "toxin" in some contexts is restricted to poisons of biological
origin. "Toxic" is not so restricted. Nor is "toxicology," the scientific
study of poisons.

TPQ

Threshold Planning Quantity (of an
EHS.) The maximum amount,
in pounds, of an EHS present at any one time at a facility during the
year. Depending on the substance, this amount can range from a lower
quantity of 1 to 1 000 pounds to an upper quantity of
10 000 pounds. If a facility has any EHS present in an
amount greater than the established TPQ, the facility must comply with
reporting provisions of EPCRA
§301, §302, and §303

A relationship between members of a set (mathematical or otherwise) such
that if the relationship holds between set members a and b, and also
between members b and c, then it also holds between a and c. Less wordy
examples are: a=b, b=c, ∴ [therefore] a=c; a<b, b<c ∴
a<c; a implies b, b implies c, ∴ a implies c. Holds for many
similar types of relationship, such as "is an ancestor of." But not all.
An example of an intransitive relationship might be "is a parent of."
Another interesting example of intransitivity is the relationship "is the
same biological species as." Since the ability to interbreed is often
used as the criterion of species membership, then so-called
ring species are intransitive with
respect to interbreeding.

Transmissibility

The transmissibility of a pathogen is its capacity for "vertical"
transmission, viz. perinatally from mother to child. Contrast with
infectivity.

TRI

Toxics Release Inventory.
EPCRA §313.
Requires certain facilities to submit a form annually to the
EPA and
SERC covering releases and
waste management of toxic
chemicals. The information is
available to the public, although it is not
up to date: there is around a two year delay in posting of results.

TSCA

Toxic Substances Control Act,
40 CFR 700–799.
Gives the EPA jurisdiction to
control the use of and exposure to industrial chemicals not subject to
other laws.

TWA

Time–Weighted Average. An arithmetic mean value taken over a
time period. Multiply each
value by the number of time units in which that value occurred, sum the
products, and divide the sum by the total number of time units.

UCS

Unified Command Structure. An expanded version of the concept
of ICS. It is a system for
managing a multi–jurisdictional emergency response situation,
made up of key officials from each affected jurisdiction plus the ICS
functional departments. A UCS is led by a Unified Commander (UC).

UEL

Upper Explosive Limit. The atmospheric
concentration of a
flammable hazardous material above which it is too rich in fuel
(deficient in oxygen) to be subject to explosion. See also
LEL. Note that
ventilation of an area
which contains a flammable substance above this concentration can
bring the concentration into the explosive range, and result in a
sudden fire or explosion. Known also as Upper Flammable Limit (UFL).

UHF

Ultra High Frequency radio
waves, specifically those with frequencies of 300-3000 MHz
(0.3-3 GHz), or wavelengths of 0.1-1 m (10-100 cm).

Ultraviolet (light)

"UV". The part of the electromagnetic
radiation spectrum that is shorter in wavelength than that of visible
light, and longer than X-rays, that
is, between about 380 and 10 nm. We distinguish several sub-bands of UV:

As indicated in the chart, most UV radiation is absorbed efficiently by
O3, and most of the shorter wavelengths (<200 nm) also by
ordinary molecular oxygen (O2). UVC wavelengths around 250 nm
are effective in killing bacteria. Sunlight in space is about 10% UV, but
absorption by the atmosphere, and particularly the ozone layer, reduces this
to 3%—mostly UVA—at the earth's surface, even at mid-day.

Unicode

For most of my computer–using life, the 7–bit ASCII character
coding was more than adequate, since I rarely had to print or display
much more than the upper– and lower–case Roman alphabet,
digits and common punctuation. The 8–bit extended version added
Greek characters and some European accented variants of Roman characters,
but not for example, Cyrillic. This webpage shows that further extensions
become desirable for many technical texts.

The solution that the computer community, partiularly the
Unicode
Consortium, arrived
at is intended to fix all such problems; in fact as many as the developers
of Unicode could imagine. Unicode characters are up to 32 bits wide.
This allows for an incredibly large set of distinct characters, of which
some 110 000 are currently in use. As an example of what this allows,
the entire set of Chinese ideographs (some 70 000 of them) fits
comfortably into a corner of Unicode, as well as all the alphabets and
syllabaries of the Indian languages, of Russian and related Slavic
languages, plus the writing systems of Thai, Japanese, Korean, Hebrew,
Arabic, Egyptian hieroglyphs, Braille and well, the writing systems of
some languages you may have never heard of. Sorry, but Klingon is not yet
officially included. Plus there is every mathematical symbol I've ever
seen in print and some I haven't. To save space, the traditional ASCII
character set still uses just one byte per character, but two or four
bytes (16 or 32 bits) can be employed for more remote areas of the
character set.

Uracil

One of the pyrimidine nucleobases in the
nucleotides of
RNA, whose structure is shown
on the right. The corresponding nucleoside is uridine; note that the
DNA equivalent is thymidine.

URL

Uniform Resource Locator. A Uniform Resource Identifier (URI) that
specifies where an identified resource is available and the mechanism
for retrieving it. A common example is a website page address; for my
site the home page URL is "http://ne9et.net/index.html". The "http" part
says to use the HyperText Transfer
Protocol to retrieve a file called "index.html" from the root level
of website "ne9et.net," and to interpret the file as written in a
variety of HyperText Markup Language—in this case, as
xhtml.

UTC

Coordinated Universal Time. What used to be called Greenwich Mean
Time (GMT) about 50 years ago. The British continue to call it GMT, even
though it no longer has anything much to do with the Royal Observatory
at Greenwich, England. It is a consensus time between a number of atomic
clocks located worldwide. It is thus no longer dependent on the slightly
erratic (and gradually slowing) rotation of the earth, and the annual
variations due to the earth's slightly elliptical orbit. The former is
accommodated by the infamous "leap seconds." As to why it's called "UTC"
rather than (say) "CUT," that's an international linguistic compromise.
FYI, revision dates and times for my web pages are given in UTC.

V (symbol)

V is the SI symbol for
volt, and v is
the symbol in physics for
velocity.

v/v

A label attached to the
concentration value of a substance in percent,
ppm, ppb or the like, that
indicates the value is concentration "by volume": so many volume units
of the substance as a fraction of the total volume of the mixture.

Vector

In physics, a vector quantity is one that has both a magnitude (amount)
and a direction (vs. a scalar quantity with only magnitude). This is
similar to the more general mathematical vector, othewise known as a rank
1 tensor.

In biology, a vector can
inter alia be an
organism that transmits a
pathogen to a host organism.

Vector graphics define an image in terms of geometric primitives such as
lines, points, and shapes. Have an advantage over raster graphics in being scalable without loss
of resolution. CAD packages use
this form of image representation.

Velocity

The instantaneous rate of change (first derivative) of the position of a
moving object with respect to time.
Symbol is v. Since position is usually represented in
physics formulas as "x," we have v=dx/dt.
"Velocity" differs from "speed" in that the direction of motion is also
significant—it is a vector
quantity. Velocity times mass is
momentum. See also
acceleration.

venom

A toxin of animal origin that
is injected into another animal's blood stream through a bite or sting
("envenomation"). Contrasted with
poison.

Ventilation

Replacement of contaminated air with air from the surrounding area.
Typically, the replacement air will be cleaner and/or contain more
oxygen.

Ventral

Towards or on the front or lower ("belly") surface of an organism.
Synonym is "inferior." Opposite of dorsal.

Ventricle

Adjective ventricular. The lower, larger chambers of the heart. Blood is
fed from the smaller atria
above them, which the ventricles then pump to the lungs (right ventricle),
and to the body (left ventricle).

Vernier (scale)

A measuring tool that allows higher resolution measurements than can be read
directly and otherwise unaided from a measuring device's native scale.
Works when the native scale is linear. Named for its developer, Pierre
Vernier, though pronounced "VER nee er." It uses a supplementary scale
adjacent to the main one, with slightly different spacing, such that
n divisions of the vernier scale cover n+1 divisions of the main scale.
N is typically 10. The vernier scale line that precisely aligns with a
main scale line indicates the interpolated final digit of resolution
more accurately than could normally be estimated by eye.

VHF

Very High Frequency radio waves,
specifically those with frequencies of 30-300 MHz, or wavelengths of
1-10 m.

Virulence, virulent

The ability of a pathogenicbiological agent to cause
disease harmful to its host,
often severe enough to incapacitate or kill the host. Virulence is
measured by the mortality rates associated with the disease, and/or by
the ability of the biological agent to invade its host's
tissues.

VOAD

Voluntary Organizations Active in Disaster. Generally refers to the
state affiliates of NVOAD.

VOC

Volatile Organic Compounds.
Organic compounds with a
"fast" evaporation rate
into the air. VOCs include substances such as benzene, toluene,
methylene chloride, and methyl chloroform.

Volatilization

A general term for the state
change of a substance into a gas. It covers both evaporation (from
liquid to gas), and
sublimation. A substance
is "volatile" if it readily undergoes volatilization at ordinary
temperatures.

Very Small Aperture Terminal. It is a two-way satellite ground station
with a dish antenna smaller than 3 m diameter.

VSMOW

Vienna Standard Mean Ocean Water. This is the standard for water used
in defining the kelvin
(and by extension Celsius)
thermodynamic temperature scale. It specifies the isotopic composition
of hydrogen (1H, 2H and 3H) and oxygen
(16O, 17O and 18O). Despite the name,
VSMOW is unlike ocean water in that it has no dissolved salts.

A label attached to the
concentration value of a substance in percent,
ppm, ppb or the like, that
indicates the value is concentration "by
weight" (loosely speaking):
so many mass units of the
substance as a fraction of the total mass of the mixture.

Wide Area Augmentation System. Primarily an air navigation aid developed
by the US Federal Aviation Administration (FAA) to augment the Global
Positioning System (GPS), with
the goal of improving its accuracy, integrity, and availability. Most
commercial GPS receivers these days include the possibility of reception
of the WAAS correction signals, making them correspondingly accurate.

WAI

Web Accessibility Initiative. An organization whose
object is to develop strategies, guidelines, and resources to help make
the Web accessible to people with disabilities. These web pages were
designed and executed with WAI guidelines in mind.

WAN

Wide Area Network. A network that provides data links for computers
that are located within a broad geographical area. Subspecies of WANs
include MANs (Metropolitan Area Networks). Contrast with
LAN.

WAP

Wireless Access Point. A device that provides access to a wireless network
for devices such as computers, using standards such as
Wi-Fi.

watt

Symbol W; named for James Watt. The
SI derived unit of power. Although popularly primarily associated
with electrical power, the watt is not defined in electrical terms, and can
be used for any kind of power: automotive engines can be (and are) rated in
watts (or kilowatts) as well as in, say, horsepower. Since the SI unit for
work/energy is the joule, the
watt is a joule per second, or
in SI base units: kg⋅m2⋅s-3.

Apart from the ampere, which
is an SI base unit, most SI electrical units include the watt directly or
indirectly as part of their definition. (Notable exception: the
coulomb, equal to an
ampere⋅second).

WEEL

Workplace Environmental Exposure Level. Guidelines of the American
Industrial Hygiene Association for substances that do not currently
have a TLV established.

Weight

The force exerted on an object
that has mass under the influence
of gravity, or of an equivalent
acceleration. Thus
gravitational weight Wg = m⋅g, where m
is mass, and g is the (local) value of the acceleration of gravity. On the
earth's surface, g is a vector of
magnitude 9.80665 m/s2, directed towards the earth's center
of gravity. A key point is that weight is properly measured in force units,
not mass ones (for example in
pounds, but not in
kilograms). Also, an object
in orbit or freefall is (nearly) weightless, but not massless. Opinions
differ on whether weight should be defined as a vector quantity (since force
is a vector), or as just the scalar magnitude of the vector. If the latter,
the formula becomes Wg = m⋅|g| . Take your pick.

WGS84

World Geodetic System, 1984 revision. This is the model of the earth's
shape used by GPS. WGS84 also
includes definition of a gravitational equipotential surface used to
define nominal sea level. A marginally interesting factoid: under WGS84,
the prime meridian no longer goes exactly through the Royal Observatory
at Greenwich, England, but about 100 m east of it.

A trademark of the Wi-Fi Alliance for a type of wireless
Local Area Network based on the
IEEE 802.11 standards. The Wi-Fi Alliance provides certification that a
wireless device is compatible with the relevant standards.

WMD

Water Management District.

WMD

Weapon(s) of Mass Destruction.

Work

In physics, equivalent to energy,
and like energy has SI units of
joules. Symbol is W. Often taken
to be the energy not dissipated as heat, thus dE=δQ − δW.
See entry on energy for further details.

WRM

Water-Reactive Material.

WWV[B]

Radio stations operated by NIST
on frequencies of 2.5, 5, 10,
15 and 20 MHz (WWV) and 60 kHz (WWVB). The WWV stations, located
near Fort Collins CO, plus the related Kekaha HI station WWVH, broadcast a
variety of information, particularly UTCtime signals. The carrier frequencies are used to
calibrate radio transceivers,
and the audio tones used are also standards (including A=440 Hz). Along
with the beeps each second, there are regular voice broadcasts that provide a
variety of technical information. The WWVB signals are used to synchronize a
variety of commercially available clocks and clock radios; these are often
loosely called "atomic" clocks. See NIST's
WWV and
WWVB web pages for details.

X (symbol)

X is used as the symbol in electronics formulas representing electrical
reactance. In physics fomulas,
x is often the symbol for spatial position.

X Window System

Based on the X11 protocols developed originally at MIT, this is a suite of
tools for developing cross-platform GUI
applications. Personal note: I wrote a great deal of code in my last years
of employment for PC users to access UNIX-based systems, using X (as it is
known for short). The PC runs an application called an X Server that takes
input from clients on the remote system over a network and renders it
graphically.

XHTML

eXtensible HyperText Markup
Language. An XML-based markup language that extends Hypertext Markup Language (HTML). By basing the web
site markup language on XML, it becomes possible to incorporate the existing
variety of XML formatting tools. The structure of XHTML is also more strictly
defined and interoperable than the rather loose HTML standards. My web site
pages are written in conformance with XHTML level 1.1.

XML

eXtensible Markup Language. A family of languages for "text markup," that
is, for encoding the structure of a text document in computer-readable form.
Commonly used XML-based languages include XHTML, RSS, SOAP, and the native
Open Office document file storage formats.

Y (symbol), Yank

Yank is the name given to the instantaneous rate of change of
force. Thus the second derivative
of momentum. Equal to
jerk times
mass:
Y=j⋅m.
Further derivatives of momentum have been named Tug (3), Snatch (4) and
Shake (5).

Z (symbol)

Z is used as the symbol in electronics formulas representing electrical
impedance.
Z or ℤ represents the set of all
integers. In chemistry, the
atomic number (number of protons in the atom) of an element.

Z list

OSHA's Toxic and Hazardous
Substances Tables Z-1, Z-2 and Z-3 of air contaminants. These tables
give the TWA,
STEL and
Ceiling values for the
listed materials.